Final answer:
The sex ratio of various countries can be influenced by government policies like China's one-child policy, access to birth control, socioeconomic factors, and cultural preferences, leading to imbalances in gender populations.
Step-by-step explanation:
The sex ratio in various countries has been influenced by several factors, including policies and cultural preferences. Among these are government policies like the one-child policy in China, which was strictly enforced until 2016 and led to a preference for male children, causing a significant gender imbalance. Additionally, policies that limit or expand access to birth control, offer tax deductions for having multiple children, and other socio-economic factors such as gender equality and educational opportunities for women, also play a role in shaping the sex ratio. For example, limiting access to birth control and a one-child policy can lead to a higher male-to-female ratio, as seen in China's past. In contrast, expanding access to birth control and educational and economic opportunities for women often result in a lower birth rate and a more balanced sex ratio.