John Graunt noted that in London over a 35-year period in the 17th century (1628–62), the birth sex ratio was 1.07; while Koreas historical records suggest a birth sex ratio of 1.13, based on 5 million births, in 1920s over a 10-year period. Other historical records from Asia too support James hypothesis. For example, Jiang et al. claim that the birth sex ratio in China was 116–121 over a 100-year period in the late 18th and early 19th centuries; in the 120–123 range in the early 20th century; falling to 112 in the 1930s.
During which century was the birth sex ratio the highest in China?
early 20th century