According to the Pew Research Center, the number of never-married Americans is at an all-time high. CDC data shows that in 2012, 1 in 5 adults age 25 or older had never been married. That's compared to 1 in 10 in 1960.
Researchers attribute the dramatic rise of never-married adults and the emerging gender gap to several factors.
Adults are marrying later in life, and there's a significant increase in adults who are living together and raising children outside of marriage.
The median age at first marriage is now 27 for women and 29 for men, up from 20 for women and 23 for men in 1960.
About 24 percent of never-married young adults ages 25 to 34 live with a partner. This trend cuts across all major racial and ethnic groups, but it is more pronounced among blacks.
Among black adults ages 25 and older, the never-married share has quadrupled over the past half century - from 9 percent in 1960 to 36 percent in 2012. For whites, the share doubled from 8 percent to 16 percent.
Fully 36 percent of blacks ages 25 and older remained single in 2012, up from 9 percent in 1960.
For whites and Hispanics, the share of never-married adults has roughly doubled over that same period. In 2012, 16 percent of whites and 26 percent of Hispanics had never married.
Why is this happening?
There are a variety of circumstances contributing to this "I Don't" mindset.
Many adult children of divorce are gun-shy about marriage. Many who watched their parents' marriage fall apart doubt their own ability to choose a good partner. They also doubt their ability to make it last.
Women in subsidized housing can lose their benefits when a man is in the home. Celebrity marriages are unstable. Many young people question their own chances for marital success when those they admire can't make it work.
Still others see marriage as a mere piece of paper with no real value.
Survey data found a deep division in public perception of marriage's role in society.
Approximately 46 percent of respondents believes that making marriage and having children a priority is better for society. But, 50 percent believes society is just as well off if marriage and children are not top priorities.
Taking age into account, two-thirds of 18 to 29 year olds believe that society is just as well off if people have priorities other than marriage and children.
Interestingly, most Americans (68 percent) still believe marriage is important if couples plan to spend the rest of their lives together.
One in five adults 25 and up have never married, yet 53 percent would like to marry some day. And, there is plenty of research indicating that healthy marriage positively impacts adults, children and society.
Perhaps millennials don't need to be convinced to invest in marriage. They may need more confidence that they can make it work - and that it's worth the effort for the success of generations to come.