Interracial dating and intermarriage has increased in the last century due to greater human mobility and multiculturalism. It should be remembered that personal preferences and the presence or absence of prejudice are irrelevant to people who are born and die in the same town or city, which was often the case before the invention of the automobile and the jet plane. Before the 20th century, with the exception of soldiers and traders, most people rarely interacted with foreigners. Even the term "interracial dating" is subject to interpretation. Often people take it to mean marriage between caucasians, asians and blacks. However, most people have strong historic, national and linguistic identities as well, which may cause more interpersonal differences than just ethnological definitions of race.