2.1. Research on state-owned capital participation

Mixed-ownership reform, as a strategic initiative for deep-level adjustment of the national economic structure and improvement of the socialist market economic system, has attracted extensive attention in academia. Early studies primarily focused on the forward mixed-ownership reform, where state-owned enterprises introduced private equity, investigating the impact of non-state shareholders on aspects such as internal control quality [16], executive compensation stickiness [17], and the economic performance of state-owned enterprises.

In recent years, with the deepening of mixed-ownership reform, reverse mixed-ownership has emerged as a significant research focus, representing another key model of ownership integration. Scholars have mainly employed empirical research methods to examine the economic consequences of state-owned capital participation, which can be broadly categorized into two dimensions: political connections and corporate governance. At the political connection level, the presence of state-owned capital establishes a direct institutional link between private firms and the government, allowing such participation to be viewed as a unique form of political affiliation [18]. By leveraging the political attributes of state-owned capital [19], private enterprises can significantly alleviate the resource constraints caused by ownership-related factors [6,20,21], thereby exerting positive effects on corporate innovation investment [22], digital transformation [7], and risk-taking [20]. However, this benefit may come at a cost, such as increased labor cost stickiness [21]. On the other hand, some studies also point out that while private firms gain access to valuable resources, they may also face pressures from government intervention, including absorbing excess employment [23] and engaging in more frequent charitable donations [24]. At the corporate governance level, state-owned capital can function as an active monitoring entity, helping mitigate the dual agency problem of private enterprises [10,25]. This not only improves the quality of corporate disclosure [26] and reduces the likelihood of misconduct [27], but also significantly curbs corporate financialization [25]. In addition, state capital involvement can further stimulate managerial innovation, thereby contributing positively to firms’ financial performance [26].

2.2. Research on supply chain stability

Another stream of literature closely related to this study focuses on supply chain stability. Prior studies have examined the economic implications of supply chain stability. From the perspective of a company’s own development, maintaining long-term and stable cooperative relationships with suppliers and customers facilitates greater access to trade credit financing [28], improve green innovation [29], and improve investment efficiency [30], all of which support enterprise innovation and stabilize production expectations [31]. Meanwhile, supply chain stability can also send positive signals externally, alleviating information asymmetry with other stakeholders, thereby increasing bank borrowings [32] and improving the enterprise’s information environment [33]. Conceptually, supply chain stability refers to the stability of the supply chain to maintain consistent operations amid external disturbances, serving as a core component of supply chain resilience [34].

Given the complex and volatile geopolitical and economic environment, supply chain stability is crucial for enterprises to cultivate competitive advantages. Currently, based on data disclosed by Chinese listed companies, the purchase and sale amounts with the top five suppliers and top five customers account for 30–40% of the annual operating revenue for most enterprises, indicating a heavy dependence on major suppliers and customers [35]. Therefore, exploring how to maintain supply chain stability has important practical significance. Baiman and Rajan (2022) argued that reducing information asymmetry between suppliers and customers significantly strengthens supply chain stability [36]. Bauer et al. (2018) conducted research on the relationship between a company’s internal control level and supply chain stability, finding that a robust internal control level can significantly reduce the occurrence of supply chain disruptions, thereby enhancing supply chain stability [37]. Chen et al. (2024) found that ESG decoupling undermines customer stability by damaging corporate reputation and exacerbating information asymmetry [38]. Jin (2025) noted that the heightened concentration of expert power within firms can deteriorate the quality of corporate disclosures, thereby indirectly undermining supply chain stability [39].

2.3. Research gap

Existing literature on supply chain stability has mainly explored influencing factors such as alleviating information asymmetry, improving internal corporate governance, enhancing ESG performance, and the involvement of venture capital in equity structures. Meanwhile, research on economic effects of state-owned capital participation, prior studies have largely focused on its impact on private enterprises’ innovation investment and digital transformation. However, in the today’s economic environment, competition among firms has increasingly shifted toward competition between supply chains. Supply chain stability, as a core indicator of a firm’s supply chain management capability, is crucial for private enterprises to withstand external risks and achieve sustainable development. Nevertheless, existing research has largely overlooked state-owned capital’s influence into the realm of corporate supply chain management. This gap may hinder a comprehensive understanding of the driving mechanisms behind supply chain stability. Therefore, it is imperative to investigate how state-owned capital participation affects the supply chain stability of private enterprises.

Considering the above research gap, this study innovatively incorporates state-owned capital participation and the supply chain stability of private enterprises into a unified research framework. It combines empowerment theory with empirical research methods. The study systematically investigates and tests the impact of state-owned capital involvement on the supply chain stability of private enterprises, as well as the underlying mechanisms. The goal is to provide a theoretical basis and decision-making reference for optimizing supply chain management through strategic equity arrangements. It also offers new empirical evidence on the interaction between state-owned capital and supply chain governance. This contributes to the high-quality development of the private economy and enhances industrial and supply chain resilience.

3.1. Resource empowerment – alleviating resource constraints

Grounded in the resource-based view (RBV), the resource empowerment provided by state-owned capital to private enterprises helps alleviate their resource constraints, thereby offering critical support for supply chain stability. The RBV posits that the heterogeneous resources possessed by firms are the core source of their competitive advantage [42]. State-owned capital participation addresses resource deficiencies in private firms by injecting scarce and valuable resources, forming the theoretical foundation of the resource empowerment mechanism. Specifically, the resource empowerment effect manifests primarily in two dimensions: financial resources and political resources, both of which are aligned with the RBV principles of “scarcity” and “value.” In terms of financial resources, state-owned enterprises, with their high credit ratings and stable funding sources, possess high-quality financial resources that are difficult for private firms to access. Once state-owned capital becomes a shareholder, private enterprises can leverage these advantages to secure more favorable loan terms, including more favorable loan interest rates and longer repayment periods when applying for bank loans or issuing bonds [43]. From the perspective of resource signaling, state-owned capital participation signals to the market that the enterprise’s quality has been endorsed by authoritative entities [24]. Backed by the credibility of state-owned capital, this signal reduces information asymmetry for external investors, enabling private enterprises to attract more external financing. For instance, after Guozhen Environmental introduced China Energy Conservation and Environmental Protection Group as a state-owned shareholder, it secured an additional credit line of 3.7 billion yuan through the group’s platform resources, significantly easing financing constraints, a clear demonstration of financial resource empowerment. In terms of political resources, the integration of state-owned and private capital fosters a “symbiotic relationship” at the institutional level, allowing private enterprises to benefit from the political connections of their state-owned shareholders. Leveraging their close ties with government agencies, state-owned shareholders can assist private firms in securing policy support, such as reduced thresholds for government subsidies [44], obtaining tax incentives, and gaining market access in regulated industries [45]. These political resources are scarce and difficult to imitate, aligning with the RBV’s definition of “strategic resources” and providing private enterprises with unique competitive advantages.

The enhancement of resource acquisition capabilities resulting from the above-mentioned resource empowerment has a direct and tangible impact on supply chain stability. In the resource-based view, “resource application capability” acts as the critical mediating mechanism. In supplier relationship management, private enterprises with ample financial resources and stable operations can offer suppliers reliable credit guarantees and substantial order commitments [46]. This cooperation model is grounded in resource advantages and fosters long-term trust from suppliers. Consequently, suppliers prioritize these firms during periods of resource scarcity. For example, stable cash flow enables timely payment for goods and services, preventing disruptions in cooperation caused by suppliers’ liquidity constraints and thereby maintaining supply chain continuity. In terms of technological innovation investment, abundant resource reserves allow private enterprises to increase spending on supply chain management technologies [47]. These may include adopting Internet of Things (IoT) solutions and advanced supply chain management software [48]. Such technological investments enhance supply chain transparency and early-warning capabilities for potential risks. By tracking real-time data on raw material transportation, inventory levels, and other key indicators, firms can identify emerging supply disruption risks and proactively adjust strategies [49]. This resource-based technological empowerment directly strengthens the supply chain’s resilience in coping with uncertainties.

3.2. Internal governance structure empowerment – Mitigating principal-agent conflicts

Agency theory suggests that state-owned capital empowers the governance structures of private enterprises. This empowerment helps reduce principal, agent conflicts by improving governance mechanisms, thereby strengthening supply chain stability. When ownership is separated from management, conflicts can arise due to different interests and information gaps. A sound governance structure helps balance the relationship between shareholders and management [50], supporting the role of state-owned capital in this process.

Specifically, governance structure empowerment operates mainly through three dimensions: First, governance structure optimization. State-owned enterprises typically possess mature governance systems and standardized management practices [51]. Their participation in private enterprises facilitates the transfer of institutional experience, assisting in clarifying the division of rights and responsibilities among shareholders, boards of directors, and management teams. From the perspective of agency theory, this clear allocation of authority and responsibility reduces the room for agents to overstep their bounds or shirk duties, directly lowering the goal divergence between shareholders and management and easing the core principle of agent conflicts. Second, an improvement in information transparency. Information asymmetry is a primary driver of principal-agent conflicts [52]. Following state-owned capital participation, SOE oversight prompts private enterprises to improve the quality and transparency of their information disclosure. By reducing shareholders’ “information disadvantage” regarding managerial actions, this shift curbs managers’ moral hazard and opportunistic behavior [9], further weakening agency tensions. Third, refinement of compensation and incentive mechanisms. State-owned capital involvement can encourage the adoption of scientific incentive and accountability systems in private enterprises [53]. On one hand, linking compensation mechanisms to shareholder returns aligns the managerial incentives with those of shareholders; on the other hand, strengthened oversight and performance evaluation mechanisms impose behavioral constraints on management [54]. Together, these dual mechanisms address principal-agent issues from both “interest alignment” and “behavioral control” perspectives, effectively reducing potential conflicts.

The mitigation of principal-agent conflicts through governance structure empowerment is directly linked to supply chain stability via three transmission channels: First, in the trust and cooperation dimension, standardized internal governance and reduced agency conflicts signal to supply chain partners that the enterprise operates in a “stable and risk-controlled” manner [55]. This signal, derived from the predictability due to governance optimization, directly enhances the trust of suppliers, distributors, and other partners. Since trust underpins long-term supply chain collaboration, its reinforcement significantly reduces the likelihood of opportunistic behavior and promotes deeper, more stable partnerships. Second, in the information sharing and strategic coordination dimension, the mitigation of agency conflicts removes barriers to internal information transmission [56], enabling the firm to share critical data such as demand forecasts and inventory levels more effectively with supply chain partners. This seamless flow of information, resulting from improved internal coordination efficiency due to governance optimization, strengthens strategic alignment among supply chain members, reduces supply disruptions caused by information delays or inaccuracies, and thereby improves overall stability [57]. Third, in the dimension of internal operations and external interactions, reduced agency conflicts directly optimize internal business processes [58], making procurement, production, and logistics decisions more efficient. This internal efficiency extends into supply chain interactions, thus reducing supply chain volatility stemming from poor internal coordination.

In summary, this study proposes the following research hypotheses:

1. H1: State-owned capital participation enhances the supply chain stability of private enterprises.
2. H1a: State-owned capital participation can enhance the supply chain stability of private enterprises by alleviating resource constraints.
3. H1b: State-owned capital participation can enhance the supply chain stability of private enterprises by alleviating principal-agent conflicts.

4.1. Data source

In 2013, the Third Plenary Session of the 18th Central Committee of the Communist Party of China proposed encouraging mixed-ownership enterprises with non-state capital as the controlling shareholder, marking the beginning of the reverse mixed-ownership reform initiative. Accordingly, this study examines A-share listed private enterprises from 2013 to 2022. Based on prior research, data were processed as follows: (1) Financial firms were excluded due to major differences in business models, regulatory environments, and supply chain structures. (2) Companies designated as ST, *ST, or those with severe data deficiencies were removed to minimize bias from financial distress or incomplete reporting. (3) Firms with state-owned shareholders holding more than 50% were excluded to focus specifically on non-controlling state-owned participation. (4) Continuous variables were winsorized at the 1% level to mitigate the influence of outliers. After these adjustments, the sample comprised 8,873 observations from 1,392 private listed companies. Unless otherwise specified, all variables used in subsequent analyses were obtained from the CSMAR and Wind databases.

4.2. Variable definition

4.3. Model construction

To examine the impact of state-owned capital participation on the supply chain stability of private enterprises, this study constructs a two-way fixed effects model (1):

(1)

Where, the subscripts i and t denote the enterprise and the year respectively; represents supply chain stability; represents the degree of state-owned capital participation in private enterprises; Controls represent all control variables; Year and Firm represent year fixed effects and enterprise fixed effects respectively; represents the random disturbance term.

5.1. Descriptive statistics

The descriptive statistics results for the main variables in this study are presented in Table 1. The variable Stability ranges from 0 to 1, indicating significant differences in supply chain stability among different private enterprises. Meanwhile, the mean value of Stability is 0.583, suggesting that at least two of the top five suppliers or customers of sample firms experienced relationship changes within the given year. In addition, the mean value of the core explanatory variable, State1,is only 0.018 with a standard deviation of 0.035, indicating low overall levels of state-owned capital participation among Chinese private enterprises, and most of them do not have state shareholders among their top ten shareholders. Higher values of State1 signals greater state-owned capital involvement. The remaining variables all fall within a reasonable range and consistent with patterns observed in existing literature.

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Table 1. Descriptive Statistics Results of Main Variables.

https://doi.org/10.1371/journal.pone.0342691.t001

5.2. Correlation analysis

This study employs the Pearson correlation test to investigate the relationship between variables. As shown in Table 2, the correlation coefficient between State1 and Stability is 0.135, which is significantly positive at the 1% level, indicating a robust positive association between state capital participation and supply chain stability in private enterprises. This provides preliminary support for Hypothesis 1.

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Table 2. Results of Correlation Analysis.

https://doi.org/10.1371/journal.pone.0342691.t002

5.3. Benchmark regression

Table 3 reports the benchmark regression results of the impact of state-owned capital participation on the supply chain stability of private enterprises. To enhance the reliability of the research conclusions, a stepwise modeling strategy is adopted, gradually incorporating control variables and fixed effects. As shown in Table 3, across all specifications, the coefficient on State1 remains positive and statistically significant at the 1% level, regardless of model adjustments. Meanwhile, as control over the model tightens, the R-squared value increases. With enhanced control, the model’s explanatory power gradually improves. From an economic perspective, taking the fourth example where all control variables and fixed effects are included, for a one-standard-deviation increase of state-owned capital participation, the supply chain stability of private enterprises increases by 0.020 (0.5713 × 0.035) units, which is a 3.42% (0.020/ 0.583) increase compared to the mean. Therefore, from either an economic or statistical perspective, state-owned capital participation has a statistically and economically meaningful positive effect on supply chain stability in private enterprises, offering initial validation of Hypothesis 1. Hypothesis 1 of this paper is initially verified.

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Table 3. Benchmark Regression Results.

https://doi.org/10.1371/journal.pone.0342691.t003

5.4. Robustness test

5.4.1. Instrumental variable method.

Endogeneity arising from potential reverse causality poses a critical challenge. State capital participation can enhance the stability of private enterprise supply chains, while private enterprises with more stable supply chains might also attract greater state investment. The instrumental variable (IV) approach introduces instruments that satisfy two core conditions. (i) strong relevance: they must be highly correlated with the endogenous regressor (State1); and (ii) exogeneity: they must influence the outcome (Stability) only through the regressor and be uncorrelated with the error term or any casual pathway. This process filters out the portion of the explanatory variable influenced by the dependent variable. It retains only its exogenous variation, enables the regression to isolate the causal effect and mitigate bias arising from reverse causality. Therefore, to mitigate potential endogeneity issues, this study conducts an instrumental variable (IV) test. Firstly, following established research practices [11,59], we adopt the industry-year average proportion of state capital participation as an instrumental variable for state capital participation (IV). The reasons are as follows: Firstly, the state capital tends to support key national industries. Therefore, the average level of state capital participation in the industry in which a private enterprise operates is correlated with the level of state capital participation that the enterprise itself can obtain, satisfying the relevance requirement. Secondly, the average proportion of state capital participation in the industry for that year is unlikely to have a direct impact on the stability of the private enterprise’s supply chain, meeting the exclusion restriction. The first-stage regression results, reported in column (1) of Table 4, show a significantly positive coefficient on the IV, confirming a strong association between the instrument and the endogenous regressor. Furthermore, the first-stage F-values exceed the empirical threshold of 10, indicating the reasonableness of the instrumental variable selection. In the second-stage, regression results presented in column (2) of Table 4. In the second stage, presented in column (2) of Table 4, the results show that the regression coefficient of State1 remains significantly positive, confirming the robustness of the baseline regression results.

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Table 4. Robustness Tests: Instrumental Variable Method, Matching Method, Difference-in-Differences (DID) Method.

https://doi.org/10.1371/journal.pone.0342691.t004

5.4.3. Difference-in-differences (DID) method.

To further mitigate the interference caused by reverse causality and sample selection bias in the research, a multi-period difference-in-differences (DID) framework is implemented to reassess the causal relationship between state-owned capital participation and increased supply chain stability of private enterprises. Specifically, referring to the approach of existing research [11], state capital entry is treated as an exogenous policy-like shock, the following DID model is specified:

(2)

Where Treat is a grouping dummy variable. If a private enterprise has received state-owned capital participation during the sample period, it is assigned to the treatment group (Treat = 1); otherwise, it is assigned to the control group (Treat = 0). Post is a time dummy variable, that equals 1 in the year of first exposure to state capital and all subsequent years, and 0 in earlier years. The definitions of the remaining variables are consistent with the benchmark regression model. The regression results are shown in column (5) of Table 4. The results indicate that the regression coefficient of Treat × Post is significantly positive at the 1% level, again suggesting that state-owned capital participation has a significant positive impact on enhancing the supply chain stability of private enterprises.

Furthermore, this study employs an event study approach to construct Model (3), aiming to examine the dynamic effects of state-owned capital participation on supply chain stability:

(3)

Where Post (n) represents the nth period before and after the first state-owned capital participation event for both the treatment and control groups. In this study, the period immediately preceding the event is set as the reference (base) period to test the parallel trends assumption, and the results are shown in Fig 1. Before state-owned capital participation, there is no significant difference in supply chain stability between the two groups of private enterprises, satisfying the parallel trends assumption. However, following state-owned capital participation, the treatment group exhibits a significant and sustained increase in supply chain stability relative to the control group, indicating a lasting positive impact of state ownership involvement.

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Fig 1. Results of the Parallel Trends Test.

https://doi.org/10.1371/journal.pone.0342691.g001

5.4.4. Alternative variable specifications.

To further verify that state-owned capital participation can increase the stability of private enterprises’ supply chains, alternative measures of both the key explanatory variable and the dependent variable are employed. First, the equity balance ratio between state-owned shareholders and non-state-owned shareholders among the top ten shareholders (State2) and whether the largest state-owned shareholder holds more than 10% of the shares (State3) are used to re-characterize the measure of state-owned capital participation. The regression results are shown in columns (1) and (2) of Table 5. The results indicate that the regression coefficients of both State2 and State3 are significantly positive. Second, in the previous sections, the average of supplier relationship stability and customer relationship stability was used to measure supply chain stability. Next, this study conducts separate regressions on supplier stability (SRS) and customer stability (CRS). The regression results in columns (3) and (4) of Table 5 show that the regression coefficients for State1 are 0.5310 and 0.6116, both of which are significantly positive at the 1% level, indicating that state-owned capital participation positively promotes both supplier and customer stability. Moreover, the regression coefficient of CRS is greater than that of SRS, suggesting that state-owned capital participation has a relatively stronger effect on customer-side relationships for private enterprises. These results indicate that the main conclusions remain robust under alternative model specifications.

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Table 5. Other Robustness Tests: Alternative Variable Specifications, Other Influencing Factors.

https://doi.org/10.1371/journal.pone.0342691.t005

5.5. Test of the mechanism of action

The positive and robust relationship between state-owned capital participation and supply chain stability motivates further investigation into the underlying mechanisms. Based on theoretical arguments of this study, two potential channels are proposed: One is alleviating pressure from resource constraints, and the other is mitigating principal-agent conflicts. To test these hypotheses, this study draws on Jiang (2022) [60] regarding the examination of underlying mechanisms and, combined with a two-way fixed effects model, constructs model (4) to test the mediating effects:

(4)

Where M represents each hypothesized mechanism variable in turn, and the rest remain consistent with the benchmark regression model.

5.5.1. Resource empowerment.

The alleviation of resource constraints can enable private enterprises to make timely payments and fulfill their contractual obligations, thereby strengthening the stability of supply chain relationships. To examine the resource empowerment mechanism, this study assesses the resource constraint pressure faced by private enterprises from two dimensions: financial resources and political resources. For financial resources, the financing constraint index (FC) is employed as its proxy variable, with a higher value indicating more severe financing constraints. For political resources, this study uses the logarithm of government subsidies plus one (Subsidy) as its proxy variable. The regression results are shown in columns (1) and (2) of Table 6. The estimated coefficient of State1 in column (1) is significantly negative, indicating that state-owned capital participation mitigates financing constraints faced by private enterprises. The estimated coefficient of State1 in column (2) is significantly positive, indicating that state-owned capital participation can increase the amount of government subsidies received by private enterprises. Sobel tests further confirm the mediating role of resource empowerment, with Z-statistics for FC and Subsidy being 2.824 and 3.321, respectively, both of which are significantly positive at the 1% level. Collectively, these findings indicate that state-owned capital participation reduces resource constraint pressure and enhances supply chain stability among private enterprises, thus supporting Hypothesis H1a. Considering the results from columns (1) to (2) collectively, it can be inferred that state-owned capital participation can alleviate the resource constraint pressure of private enterprises and thereby enhance their supply chain stability. Hypothesis H1a is verified. To address potential endogeneity between state-owned capital participation and resource empowerment, lagged resource variables are incorporated into the model, and system GMM estimation is applied. The results in Table 6, Panel B, columns (1) and (2), show that the effect of state-owned capital participation on resource empowerment is consistent with Panel A and passes the AR (1), AR (2), and Sargan tests. Therefore, even after considering endogeneity, hypothesis H1a is supported.

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Table 6. Results of Mechanism of Action Testing.

https://doi.org/10.1371/journal.pone.0342691.t006

6.1. Heterogeneity analysis based on bank-enterprise relationships (From the Perspective of Inter-Organizational Relationships)

From the standpoint of bank-enterprise relationships, firms with such ties can typically secure higher credit limits [20], thereby alleviating the financing constraints and improving their financial status. Consequently, strong bank-enterprise relationships may partially substitute for the financial benefits brought by state-owned capital participation, weakening its incremental impact on financial improvement. Therefore, we hypothesize that the positive effect of state-owned capital participation on supply chain stability is more pronounced for private enterprises lacking bank-enterprise relationships. To test this hypothesis, this study follows the approach of existing research [62] and divides the research sample into two groups: those with and without bank-enterprise relationships. A firm is classified as having a bank-enterprise relationship if it meets any of the following criteria: bank-background executives, banks holding shares in the enterprise, or the enterprise holding shares in a bank, otherwise, it is considered not to have such a relationship. The regression results, reported in columns (1) and (2) of Table 7, indicate that the estimated coefficient of State1 is not significant in the sample of private enterprises with bank-enterprise relationships, but it is significantly positive in the sample of private enterprises without bank-enterprise relationships. This suggests that, the effect of state-owned capital participation on enhancing supply chain stability is stronger for private enterprises without established bank ties.

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Table 7. Results of Heterogeneity Tests: Bank-enterprise Relationship Grouping and Product Advantage Grouping.

https://doi.org/10.1371/journal.pone.0342691.t007

6.2. Heterogeneity analysis based on product advantages (From the Intra-Organizational Perspective)

Product advantages determine an enterprise’s bargaining power and strategic position in transactions. Upstream suppliers are more inclined to allocate resources to firms with strong product advantages, as they benefit from association with reputable brands. Downstream customers seek technologically advanced and higher-quality inputs to strengthen their own competitiveness and expand market share. Therefore, compared to private enterprises with higher product advantages, those with lower product advantages are less preferred as partners by upstream and downstream enterprises, making it harder for them to maintain stable supply chain partnerships. As a result, this study infers that state-owned capital participation increases supply chain stability in private enterprises, with a more pronounced effect for those with lower product advantages. To examine this, this study divides the research sample into two groups using the industry annual median of main business revenue growth rate: private enterprises with higher product advantages and those with lower product advantages. The groups are then estimated separately. Regression results in columns (3) and (4) of Table 7 show that the coefficient of State1 is significantly positive for private enterprises with lower product advantages but not significant for those with higher product advantages. This supports the view that the stabilizing effect of state-owned capital participation is more evident in private enterprises with lower product advantages.

6.3. Heterogeneity analysis based on internal control levels (From the Intra-Organizational Perspective)

Internal control quality reflects corporate governance and plays a critical role in determining agency costs within firms [63]. A well-functioning internal control system curbs opportunistic behavior of controlling shareholders and management. It also reduces the likelihood of concealing adverse information and enhances the quality of information disclosure [64]. Therefore, strong internal control can attenuate the governance-enhancing effect of state-owned capital participation in private enterprises. Based on this reasoning, we hypothesize those private enterprises with weaker internal control experience a more pronounced improvement in supply chain stability following state-owned equity participation, compared to those with stronger internal control. To test hypothesis, we use the internal control index published by DiBo Company as a measure of internal control level. The research sample is divided into two groups based on the annual median: enterprises with better internal control and those with poorer internal control systems. Grouped testing is conducted. The regression results presented in columns (1) and (2) of Table 8 show that the coefficient on State1 is significantly positive for the group with poorer internal control, but insignificant for the group with better internal control. This suggests that the positive effect of state-owned capital participation on supply chain stability is more pronounced among private enterprises with weaker internal governance systems.

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Table 8. Results of Heterogeneity Tests: Internal Control Group and Media Negative Reporting Group.

https://doi.org/10.1371/journal.pone.0342691.t008

6.4. Heterogeneity analysis based on negative media coverage (From the Extra-Organizational Perspective)

Media coverage serves as a crucial channel through which external stakeholders obtain corporate information. Compared to positive media reports, negative media coverage attracts more attention from stakeholders, including upstream suppliers and downstream customers [65]. Once adverse information such as poor financial performance appears in negative reports, it can trigger pessimistic expectations among supply chain partners, thereby undermining the stability of corporate supply chains. Considering this, we hypothesize that compared to private enterprises with fewer negative media reports, the positive effect of state-owned capital participation on the supply chain stability of private enterprises is more pronounced in those with more negative media reports. To verify this theoretical inference, the sample is split into two groups based on the annual median number of negative online media reports about each firm, and subgroup analyses are performed. The regression results in columns (3) and (4) of Table 8 indicate that estimated coefficient of State1 is insignificant in the low-negative-media group but significantly positive in the high-negative-media group. This suggests that compared to private enterprises with fewer negative media reports, the positive effect of state-owned capital participation on the supply chain stability of private enterprises is more evident in those with more negative media reports, thereby confirming the theoretical inference.

However, recognizing the potential limitations and biases that may arise from using grouping variables for heterogeneity, The interactive fixed effects in the model were controlled. The results are shown in Table 9. As shown in Table 9, incorporating the interactive fixed effects (Year × Ind) does not alter the conclusions of this paper.

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Table 9. Heterogeneity Test Results (with interactive fixed effects included).

https://doi.org/10.1371/journal.pone.0342691.t009

7.1. Conclusions

Using data from A-share listed private enterprises from 2013 to 2022 and drawing on the empowerment theory, this study empirically examines the impact of state capital participation on the stability of private enterprise supply chains. The following conclusions are drawn: First, we develop a theoretical framework explaining how state capital involvement enhances supply chain stability, providing a theoretical reference for developing countries to introduce state capital and improve supply chain stability when private enterprises experience fluctuations in their supply chain stability. Second, state capital participation can increase the stability of private enterprise supply chains. This conclusion remains robust across a series of tests, including the instrumental variable method, matching method, difference-in-differences method, alternative variable measures, subsample regression, and interaction fixed effects. Third, the mechanism test reveals that the improvement stems from the alleviation of resource constraints and principal-agent conflicts within private enterprises. Finally, for those private enterprises that lack bank partnerships, have weak product advantages, poorer internal control, and more negative media coverage, the positive impact of government capital participation on the stability of the private enterprise supply chain is more significant. This has policy implications for optimizing the allocation of state capital.

7.2. Implications

The findings of this study carry important policy implications and practical value in deepening the reverse mixed-ownership reform and strengthening the resilience of private enterprise supply chains. For policymakers, given the significant positive effect of state-owned capital participation on the supply chain stability of private enterprises, it is advisable to further refine the implementation framework of reverse mixed-ownership reform. On the one hand, differentiated mechanisms for state-owned capital involvement should be established. Targeted support policies can be introduced for private enterprises facing weak banking relationships, limited product competitiveness, inadequate internal controls, or predominantly negative media coverage. Through measures such as tax incentives and simplified approval procedures, capital state-owned capital can be directed more precisely to areas of greatest need, thereby alleviating resource constraints and promoting governance upgrades. For example, private enterprises encountering financing difficulties can be encouraged to access state-owned capital via equity financing, supported by resource-matching platforms that facilitate connections with critical upstream and downstream supply chain partners. On the other hand, a dynamic regulatory system for state-owned capital participation should be constructed. While leveraging its capacity to enhance resources and optimize governance, reasonable limits on shareholding ratios and well-defined boundaries for administrative intervention must be set to prevent excessive interference. This ensures that improvements in supply chain stability arise from enhanced operational efficiency rather than external coercion. For private enterprises, it is crucial to proactively seize opportunities arising from the reverse mixed-ownership reform and formulate state-owned capital introduction strategies tailored to their own operational weaknesses. Firms with limited resource acquisition capabilities can establish long-term, stable resource supply channels by introducing state-owned capital and leveraging its credit endorsement to strengthen collaboration with suppliers and customers. Enterprises with internal governance deficiencies can utilize the participation of state-owned capital to enhance corporate charters, refine board structures, and mitigate the adverse effects of principal-agent conflicts on supply chain cooperation. For instance, establishing regular communication mechanisms between state-owned shareholder representatives and management can enhance decision-making transparency and execution efficiency. Additionally, industry associations can serve as intermediaries by identifying common supply chain pain points of private enterprises, building matchmaking platforms to connect state-owned capital with private firms, and organizing training programs on governance optimization. Such initiatives can facilitate the translation of research findings into practice, enabling private enterprises to build more resilient supply chains in complex market environments and supporting the sustained and healthy development of the private economy.

This study has several limitations. First, it relies on data from China’s Shanghai and Shenzhen A-shares to examine the impact of state capital participation on the stability of private enterprise supply chains. However, by focusing solely on listed companies, many non-listed private enterprises are overlooked. These enterprises are often concentrated in sectors such as small-scale manufacturing and traditional services, which are integral parts of the national economy. Therefore, the research results may not capture how state-owned capital participation influences supply chain stability in these industries, potentially leading to biased assessments of its role of state capital participation and an incomplete understanding of different industry characteristics on the relationship between state capital participation and supply chain stability. Due to constraints in data accessibility, we are currently unable to conduct research using samples of non-listed enterprises. We hope to address this limitation by incorporating broader enterprise populations in future work.