What percentage of known societies has rules requiring that sexual involvement take place only within marriage?

The answer is "15%".

This brings us to the anthropological definition of the marriage where certain agreement allows an individual to involve in certain rights and obligations. A large part of human society do not strictly regulate a person’s sexual practices, some are permissive and some are semi permissive but the fact remains that 15 percent constitutes a minority which requires that sexual involvement take place only within marriage

 

Ghana, first of the great medieval trading empires of western africa (fl. 7th–13th century). it was situated between the sahara and the headwaters of the sénégal and niger rivers, in an area that now comprises southeastern mauritania and part of mali.

Afederal parliamentary republic is  unlimited.