About the Authors
Department of Demography, University of California, Berkeley, California, United States of America
The author has declared that no competing interests exist.
Conceived and designed the experiments: RS. Performed the experiments: RS. Analyzed the data: RS. Contributed reagents/materials/analysis tools: RS. Wrote the first draft of the manuscript: RS. Contributed to the writing of the manuscript: RS. ICMJE criteria for authorship read and met: RS. Agree with manuscript results and conclusions: RS.