Mark Regnerus at The Washington Post argues that people shouldn't wait long to get married. By people he means women.

Marriage will be there for men when they're ready. And most do get there. Eventually. But according to social psychologists Roy Baumeister and Kathleen Vohs, women's "market value" declines steadily as they age, while men's tends to rise in step with their growing resources (that is, money and maturation). Countless studies -- and endless anecdotes -- reinforce their conclusion. Meanwhile, women's fertility is more or less fixed, yet they largely suppress it during their 20s -- their most fertile years -- only to have to beg, pray, borrow and pay to reclaim it in their 30s and 40s.

Great. Not only do women have escalated fears of ending up unmarried in their mid 30s, there are countless studies to reinforce their fears! This is what pushes women to the brink of desperation. It's this very study that coaxes women to take action and pressurize their boyfriends. Some benefit from it's fruitful result whilst others think of jumping off a ship at sea, thus deserting their aging girlfriends to start all over again. This is what contributes to the 'psycho girlfriend' effect, I swear.

The age gap between spouses is narrowing: Marrying men and women were separated by an average of more than four years in 1890 and about 2.5 years in 1960. Now that figure stands at less than two years.

...Most young women are mature enough to handle marriage. According to data from the government's National Survey of Family Growth, women who marry at 18 have a better shot at making a marriage work than men who marry at 21. There is wisdom in having an age gap between spouses. For women, age is (unfortunately) a debit, decreasing fertility. For men, age can be a credit, increasing their access to resources and improving their maturity, thus making them more attractive to women.

There has to be a reason to why 18 year olds are not encouraged to marry, especially to much older men. In the 21st century women have to learn to fend for themselves AND secure their future stock with a potential husband.

Many relationships take years before marriage. A woman's position in a relationship is never secure enough - and you wonder why there are so many insecure women out there. If she dates  a man for 5 years and turned 30 when he decides to dump her for whatever reason, she's wasted 5 years of her life waiting to marry this guy, and will have to begin all over again. By the time she does settle down with a new husband, family and all that sparkle, she'll probably be reaching her mid 30s.

And what do men have to do? Yes. Work, earn the big bucks and (naturally) age handsomely until they feel the time is right to settle down.