Final answer:
Without specific demographic data for all countries, it is challenging to determine which country had the largest cohort of females aged 16 in 2000. However, countries with higher development and gender equality, like those in Western Europe and North America, may have had larger cohorts compared to countries with educational gender disparities.
Step-by-step explanation:
An explanation considering the provided information is that in regions like Afghanistan, Benin, and Nigeria, the literacy rates and schooling for young females were significantly lower than for males. The data suggests that in countries with lower literacy rates for females, the cohort sizes for females would be likely smaller due to barriers preventing them from continuing education. We also know that in the United States, there was a different situation, with population data from the U.S. Census showing gender ratios and age distributions. If we consider education as a proxy, countries with higher female literacy and education levels may have had larger female cohorts aged 16 due to better access to education for girls.
Keeping these factors in mind, it might be reasoned that countries with higher levels of development and gender equality, such as those in Western Europe and North America, would have larger cohorts of 16-year-old females compared to countries with significant gender disparities in education.