Final answer:
The question does not provide data for specific years, thus making it challenging to determine which country had the largest percentage of entrepreneurs between 18 to 64 in 2012. However, based on demographic trends and economic structures, a developing country with a younger population and higher entrepreneurship rates seems more plausible than a high-income aging nation.
Step-by-step explanation:
The question inquires which country had the largest percentage of individuals age 18 to 64 that were active in starting or managing a business in 2012. The provided information suggests that economically developing countries might exhibit a fairly even distribution of individuals in all age groups and have a higher propensity for entrepreneurial activity due to the demographic structure and economic institutions varying from high-income countries. Meanwhile, high-income nations have an aging population, and their industry structure typically features a smaller percentage of GDP coming from agriculture compared to developing nations.
When considering that a country likely to have the largest percentage of entrepreneurs is one with a young adult population, high-income countries with a higher proportion of elderly and less agricultural contribution to GDP might not be the leading candidates. Therefore, among the options given, countries like China, with their impending "aging boom," may not be the correct answer. Instead, an economically developing country with a larger proportion of youth and young adults would be more probable.