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Season of birth in Puerto Rico: Rethinking changes in patterns using 90 years of births occurring under US occupation
Alexis R Santos-Lozada1, Wilmarí De Jesús Álvarez2
1Department of Human Development and Family Studies, Pennsylvania State University, State College, PA, USA.
Biodemography and Social Biology
|October 15, 2025
Summary
Birth seasonality in Puerto Rico has shifted over time, with recent changes aligning with economic transitions. Further research should explore the impact of economic shifts on these evolving birth patterns.
Area of Science:
- Demography
- Public Health
- Sociology
Background:
- Birth seasonality exhibits temporal variations influenced by various factors.
- Understanding these patterns is crucial for public health planning and demographic analysis.
Purpose of the Study:
- To examine historical birth seasonality in Puerto Rico from 1935 to 2024.
- To investigate potential shifts in birth patterns during periods of economic transformation.
Main Methods:
- Compiled monthly birth counts for over 5.64 million births.
- Utilized data from U.S. agencies, a prior publication, and the Puerto Rico Vital Statistics System.
- Calculated seasonal indices and modeled 5-year patterns using LOESS curves.
Main Results:
- Identified four distinct seasonal birth patterns between 1935 and 2024.
- Observed a shift from an April-May peak (1943-1949) to an August-October peak (1950-1954).
- A stable pattern with a second-half peak persisted until ~2010, followed by increased variability and a persistent August-November peak.
Conclusions:
- Observed changes in birth seasonality correlate with economic transitions under U.S. occupation.
- Future research should investigate the role of economic shifts in shaping birth seasonality.
- Re-evaluation of cultural or media influence hypotheses is warranted.
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