<P> Housing in urban areas may include more apartments and semi-attached homes than in the suburbs or small towns . Aside from housing, the major difference from suburban living is the density and diversity of many different subcultures, as well as retail and manufacturing buildings mixed with housing in urban areas . Urban residents are also more likely to travel by mass transit, and children are more likely to walk or bicycle rather than being driven by their parents . </P> <P> Couples often meet through religious institutions, work, school, or friends . "Dating services," services that are geared to assist people in finding partners, are popular both on and offline . The trend over the past few decades has been for more and more couples deciding to cohabit before, or instead of, getting married . The 2000 Census reported 9.7 million different - sex partners living together and about 1.3 million same - sex partners living together . These cohabitation arrangements have not been the subject of many laws regulating them, though some states now have domestic partner statutes and judge - made palimony doctrines that confer some legal support for unmarried couples . </P> <P> Adolescent sex is common; most Americans first have intercourse in their teens . The current data suggests that by the time a person turns 18, slightly more than half of females and nearly two - thirds of males will have had intercourse . More than half of sexually active teens have had sexual partners they are dating . Risky sexual behaviors that involve "anything intercourse related" are "rampant" among teenagers . Teen pregnancies in the United States decreased 28% between 1990 and 2000 from 117 pregnancies per every 1,000 teens to 84 per 1,000 . The US is rated, based on 2002 numbers, 84 out of 170 countries based on teenage fertility rate, according to the World Health Organization . </P> <P> Marriage laws are established by individual states . Same - sex marriage is legal in the United States . </P>

In the united states class membership is most influenced by which of the following