The study found that 40% of children in the United States would live in a cohabiting household by age 12, and children born to single mothers were more likely than those born to married mothers to live in a cohabiting household.
The percentage of women ages 19−44 who had ever cohabited increased from 45% in 1995 to 54% in 2002.
As a result, the patterns of family life have started to change: marriage rates have declined, and marriage was postponed to a later age.
A low sex ratio would mean there are many more women than men, resulting in differing societal values and acceptable behaviors. When given a survey of the reasons why they cohabit, most couples listed reasons such as spending more time together, convenience based reasons, and testing their relationships, while few gave the reason that they do not believe in marriage.The rise in cohabitation is part of other major social changes such as: higher divorce rate, older age at first marriage and childbearing, and more births outside marriage.Factors such as secularization, increased participation of women in the labor force, changing in the meaning of marriage, risk reduction, individualism, and changing views on sexuality have been cited as contributing to these social changes.For instance, in the European Values Study (EVS) of 2008, the percentage of respondents who agreed with the assertion that "Marriage is an outdated institution" was 37.5% in Luxembourg, 35.4% in France, 34.3% in Belgium, 31.2% in Spain, 30.5% in Austria, 29.2% in Germany, 27.7% in Switzerland, 27.2% in Bulgaria, 27.0% in the Netherlands, 25.0% in Slovenia.The fact that many couples choose to live together without formalizing their relation is also recognized by the European Union.Today, cohabitation is a common pattern among people in the Western world.In Europe, the Scandinavian countries have been the first to start this leading trend, although many countries have since followed.There has also been a change in modern sexual ethics, with a focus on consent, rather than marital status (i.e.decriminalization of adultery and fornication; criminalization of marital rape), reflecting new concepts about the role and purpose of sexual interaction, and new conceptualizations of female sexuality and of self-determination.In 2001, researchers compared teenage children living in a cohabiting household against peers in single-parent households.The results showed Caucasian and Hispanic teenagers had lower performance in school, greater risk of suspension or expulsion than peers from single-parent households, and the same rate behavioral and emotional problems.