Which country is noted for having the highest percentage of elderly individuals?

Japan is noted for having the highest percentage of elderly individuals among the options provided. This phenomenon can be attributed to several factors unique to Japan, including a combination of high life expectancy and low birth rates. The country has one of the longest life expectancies in the world, with significant advancements in healthcare, nutrition, and living standards contributing to this longevity.

Additionally, cultural factors in Japan emphasize respect for the elderly and societal support for seniors, leading to a larger segment of the population being older. These aspects help to solidify Japan's position as the country with the highest percentage of elderly individuals, distinguishing it from the other countries listed.