OP, please see the link below. It is an article that deals with the work of Fuller and Goldstone who have studied "population bulges". Essentially, a large population of young unemployed men correlates with civil wars and may have played a role in WWI and WWII as well as the Marxist regime changes in Latin America.

Between 1970 and 1999, 80 percent of civil conflicts occurred in countries where 60 percent of the population or more were under the age of thirty, according to the PAI report. Today there are sixty-seven counties with youth bulges, of which sixty of them are experiencing social unrest and violence.

http://www.cfr.org/world/effects-youth-bulge-civil-conflicts/p13093

Sorry, we don't allow throughout history questions. These tend to produce threads which are collections of trivia, not the in-depth discussions about a particular topic we're looking for. If you have a specific question about a historical event or period or person, please feel free to re-compose your question and submit it again.