Abstract:Due to its daily expanding population since 1980s, China executed a strict birth control policy which produced significant influence and generated much discussion. This paper focuses on the imbalanced sex ratio at birth resulting from the one-child policy. The authors attempt to explain the regional disparity of the sex ratio at birth using the methods of GIS and spatial analysis, with the county-level city as a unit of analysis and the population census of the year 2000. Research shows that places with the phenomenon have dynamic sex ratios at birth, and the spatial distribution is non-random. Generally, there are high sex ratios at birth in regions with large Han populations, high population densities, high per-capita incomes, large birth orders, and stricter birth control regulations. Notably, the influence of the neighborhood effects is well evident. This means that after controlling socioeconomic and ethnic variables, there are still clear evidence of agglomeration; this may be due to the imitation, learning, and idea diffusion between neighboring regions, or a natural result of location-specific cultures.