Why is the US marriage rate falling sharply?

For the first time in memory, unmarried Americans will soon outnumber those who are married, according to the latest research. So is this a watershed moment?

At first glance it would appear that, in common with many Western countries, marriage is in terminal decline in the United States.

In 1960, 72% of all American adults were married; in 2010 just 51% were, according to the Pew Centre. The number dropped sharply by 5% in the most recent year, 2009-10.

"I think we are on the cusp of seeing marriage becoming less central to our life course and in framing the lives of our nation's children. So I think it is a major moment in that regard," says Bradford Wilcox, director of the National Marriage Project and a sociology professor at the University of Virginia.

Americans are certainly waiting longer before they tie the knot - the average age for a first marriage is at an all-time high of 26.5 years for women and 28.7 for men - or else opting to cohabit, live alone or not re-marry when they get divorced.

In the UK, women are, on average, waiting until the age of 30 before getting married, while the average age of a UK bridegroom is 32. In both countries the number of weddings is at an all-time low.

"We had been together for a while by then, already, and just wanted to celebrate it.

"We just felt really strongly about being together forever and working at it, with all the difficulties that that might include.

"We are a very modern couple, we have very progressive views on a lot of things.

"I am not really sure that human beings are destined to be with the same person for the rest of their lives.

"My commitment to Chris is to try and to work as hard as we can to make it work because we both gain something out of that."

Chicago Tribune syndicated advice columnist Amy Dickinson believes the increase in no-fault divorces and tougher child support laws are two reasons behind the falling popularity of married life in America.

"It is no longer necessary to be married to someone in order to pursue financial support and I believe this has had a huge impact on couples who have children together and, let's say, 20 years ago would get married in order to establish legitimacy and then, hence, get financial support."

In some communities single parenthood is now the norm, she argues, and Americans have become more comfortable with "non-traditional" households.

America also has the world's highest divorce rate - and that has undoubtedly shaken the confidence of many young people in the institution of marriage.

Rhyan Romaine and her partner Seth have been together for six years but have resisted pressure from friends and family to rush into marriage.

"Seth comes from a family of divorce and has seen how it's affected his life and his family.

"He says he couldn't imagine even thinking about marriage until we had been together for 10 years and I said as long as we are happy together we will stay together," says Miss Romaine.

"I think it's a fear that I have too, even though my parents are married. It's scary, having seen personal friends who have got married right out of college and who now are in their early thirties and dating again."

But Miss Romaine, a regional grant director for the American Loan Association, believes there is still a "lot of pressure" on young women to get married in America, where the idealised, fairytale wedding remains a staple of Hollywood romantic comedies and reality TV shows.

"I call it the 'marriage crazy'," she says. "All of a sudden this fever comes over women at a certain age. They get to about 24 or 25 and they have to hurry up and get married."

For many young people, marriage is simply the next item on their personal "checklist" after high school, college and career, she argues.

The Pew Centre research, which suggests marriage is falling out of favour far less quickly among college graduates than less educated groups, would appear to bear this argument out.

"Women don't necessarily need a husband to make ends meet or to raise children. They can do a lot of these things on their own.

"Our definition of what you want in a husband has changed. At one time it was a nice enough dude who is also going to support you.

"In this day and age we really have this glorified notion of the soulmate. This needs to be a life partner, a best friend, a lover, everything in one.

"We are cynical but we have this really idealised notion of what a marriage should be still, and it's almost impossible to achieve that. Nothing is that perfect."

Nearly two-thirds of American adults with college degrees (64%) are married, compared with just 47% among those with a high school education. That is in sharp contrast to 1960, when the most educated and the least educated were about equally likely to be married.

"There has been a realisation among college-educated Americans that marriage is actually a pretty good idea, even if they don't like to talk about it in public," argues Bradford Wilcox.

"On things like abortion, on hot-button global social issues, Americans who are college educated are more liberal.

"But when it comes to thinking about how they are going to govern their own lives, their own family lives, our sense from the data is that they are more marriage-minded, they are more conventional about family life."

Mr Wilcox, whose Virginia University team researched the impact of the recent recession on American marriages, is concerned that marriage is "withering" among middle and lower income groups, with potentially disastrous effects on American society and the economy.

"I think we are moving more towards a classically Latin model, where the powerful and the privileged have strong, stable families and access to decent income and decent assets. And everyone who is not in that upper third is worse and worse off."

But perhaps it is a little premature to write the obituary for the American marriage just yet.

The sharp 5% decline in the number of new marriages in the US between 2009 and 2010, revealed by the Pew research, may simply be down to short-term economic factors.

With the cost of the average wedding running at about $20,000 (£12,946) many couples are opting for a longer engagement to give them more time to save up, according to Kyle Brown, of the American Bridal Association, which represents America's multi-billion dollar wedding industry.

But, he adds, his members have noticed "an increase in the beginning process of wedding planning, on items such as gowns, in the past three months".

"I would expect to see an uptick in the number of weddings in 2012 and 2013," he says. "It is purely down to economics."