Fig 1.
Study selection flowchart.
Fig 2.
Evolution of transparency indicators over time.
Only the last decade (2013–2022) is shown, since there were few eligible articles before 2013 and confidence intervals for these earlier years are very wide. * Denotes a statistically significant time trend at p<0.005.
Table 1.
Categorical characteristics of studies evaluated manually and their relationship with transparency indicators.
Table 2.
Continuous characteristics of studies evaluated manually and their relationship with transparency indicators.