# Understanding fertility trends in a cohesive high-fertility population within a low-fertility environment > **NIH NIH K99** · PENNSYLVANIA STATE UNIVERSITY, THE · 2024 · $137,160 ## Abstract Project Summary Western populations collectively responded to historically contingent, society-wide developments in the 19th and 20th centuries by reducing births to record-low levels. However, a minority of Westerners, largely ethnic sectarian religions, have maintained pre-transition fertility levels despite exposure to contexts that motivate fertility decline. How have these populations—conspicuous among them being the Amish—maintained high birth rates? Decades of sporadic research suggest that high birth and low attrition rates explain the unabated 20-25 year Amish population doubling time. Yet, it is less clear why Amish women maintain high birth rates and, perhaps more revealing, why births vary so widely among them, with community-level completed birth rates ranging from approximately 4 to 12. Occasional cross-sectional studies suggest that multiple variables—including household head occupation, religious differences, and individual status— predict Amish birth rates, but what these results mean, exactly, remains educated guesswork. This project overcomes past barriers and delivers new knowledge by making two ground-breaking contributions to Amish demography research. First, this project develops a large population-wide, time-sensitive dataset that will permanently transition Amish demography research from limited, single-site, cross-sectional analyses to full-scale, continent-wide, time-sensitive analyses. This transition will substantially advance the scope and interpretability of statistical predictors of births. This longitudinal database pulls information from Amish-produced population record books that provide extensive documentation of vital events, sociocultural information, and geocodable addresses at the household level. These geographically referenced data will then be linked to publically available contextual data. The launch-point for this database is my cross-sectional Amish population dataset, which incorporates 71 current record books with information about 54,731 unique Amish households (estimated at about 270,000 individuals), covering approximately 89.6% of all Amish in North America. The proposed longitudinal database will use all editions of three major directory sets, piloting the process of eventually incorporating all editions of all Amish directories. Second, this project will validate the data by testing population growth explanations, beginning with articulation of population structure trends over time. This project will then test the relative influence of competing fertility theories by disentangling the effects of Amish-internal versus external structural-cultural forces. Namely, are birth differences more the product of Amish-internal differences in spite of contextual socioeconomic development or is birth variation more the product of relative isolation from society-wide structures in spite of Amish internal demarcations? To test these competing theories, I will employ this project’s internally linked, geograp... ## Key facts - **NIH application ID:** 10808419 - **Project number:** 1K99HD111665-01A1 - **Recipient organization:** PENNSYLVANIA STATE UNIVERSITY, THE - **Principal Investigator:** Cory Anderson - **Activity code:** K99 (R01, R21, SBIR, etc.) - **Funding institute:** NIH - **Fiscal year:** 2024 - **Award amount:** $137,160 - **Award type:** 1 - **Project period:** 2024-09-15 → 2026-08-31 ## Primary source NIH RePORTER: https://reporter.nih.gov/project-details/10808419 ## Citation > US National Institutes of Health, RePORTER application 10808419, Understanding fertility trends in a cohesive high-fertility population within a low-fertility environment (1K99HD111665-01A1). Retrieved via AI Analytics 2026-05-27 from https://api.ai-analytics.org/grant/nih/10808419. Licensed CC0. --- *[NIH grants dataset](/datasets/nih-grants) · CC0 1.0*