Extraversion and introversion
At one time, extroverts were thought to make up almost three quarters of American society. In more modern times, however, researchers have been able to ascertain that the number of introverts almost equals the number of extroverts in the country. Interestingly, also, the prevalence of both types varies from country to country, with certain nations (Scandinavian countries, Japan) favouring introversion and others (most notably America) favouring extroversion.