Final answer:
The approximate percentage of the nation's population 16 years and older that is functionally illiterate can vary depending on the country and specific data sources.
Step-by-step explanation:
The approximate percentage of the nation's population 16 years and older that is functionally illiterate can vary depending on the country and specific data sources. According to the information provided, there are several different literacy rates mentioned for different countries and age groups. For example, Afghanistan has a literacy rate of 28.1 percent overall, while the literacy rate for women in Afghanistan is 12 percent. It's important to note that illiteracy rates can change over time due to factors such as access to education and improvements in literacy programs.