What do Britney Spears and George Bush have in common? They both believe in the "sanctity of marriage". That's what Spears told MTV after her snap decision to get married and then unmarried in the new year, and that's why in today's State of the Union address President Bush will announce a plan to spend $US1.5 billion ($2 billion) promoting marriage.
It is actually Spears who is in tune with the times. Like Spears in the cold light of day, few American women now believe they are ready for marriage at 22. Most now wait until they are at least 25, and most Australian women wait until they are at least 27. But just a couple of decades ago marriage at Spears's age was typical.
Something has made us much more wary about getting hitched. Economists have come up with at least three explanations, one of which points some of the blame at the President himself...
(If you find the whole idea of economists analysing marriage offensive, I sympathise. My marriage is the result of deep love rather than a calculation of costs and benefits. Nevertheless, economists believe we act as if we perform calculations, and they say the financial ones account for about one third of a typical decision to marry.)
The advent of the contraceptive pill removed one big non-financial cost of not getting married. As the Harvard economist Claudia Goldin puts it, from then on you could "put off marriage while not having to put off sex". The marriage rate began falling and the marriage age began rising from the moment the pill became widely available around the start of the 1970s.
But the pill did more than make it easier to delay marriage. Goldin says it made it realistic suddenly for large numbers of young women to take on major university courses such as business, law, dentistry and medicine. Before the pill they faced a high chance of getting pregnant during a five-year degree and wasting their money.
One decade after the arrival of the pill the proportion of US dental students who were women had climbed from 1 per cent to 19 per cent; the proportion of law students had climbed from 4 per cent to 36 per cent. This pushed out the age at which those women made themselves available for marriage, and also increased the potential pay-off for men who waited. They might snare a doctor.
But something else is needed to explain the continuing slide in the rate of marriage in more recent decades. Since 1980 the marriage rate among Australian women has halved. It might be that Australian women are becoming more acquainted with some of the less publicised facts about marriage.
It is widely believed that people who are married earn more, are happier and live longer than people who are single or merely "living together". But a closer look shows that in most studies the increase in earnings applies only to men and that while marriage makes both sexes happier, men get the bigger benefit. And when it comes to longevity, marriage can actually harm women.
A landmark survey conducted by Warwick University in Britain concluded last year that married men were "a remarkable 10.6 per cent" less likely to die in any given year than men who had never married. Married women received no such protection.
Worse, women who had married and then got divorced were 7.2 per cent more likely to die in any subsequent year; women who were widowed, were 3.8 per cent more likely to die.
For women concerned about a long life the evidence suggests that it is best to either not get married, or if you have done so, stay married.
And here is the economists' third explanation for the continuing slide in marriage rates, the one with direct and uncomfortable implications for the policies of George Bush, and for that matter John Howard: incomes in the US and Australia are becoming less equal.
In the US Bush pushed the process along in 2001 and 2003 with very big tax cuts directed at the already rich.
Increasing inequality means, in the words of Hebrew University economists Eric Gould and Daniele Paserman, "an increase in the dispersion of husband quality". There is now a greater potential pay-off for women in Waiting for Mr Right, to use the title of the paper just published by Gould and Paserman.
They use census data to rank 300 US cities. The most unequal city is Stamford, Connecticut, just north of New York City. It happens to also be the city with the highest proportion of women in their upper 20s who are not yet married (waiting for Mr Right).
Gould and Paserman find that female singleness closely follows male wage inequality, both between different cities and over time. As US male incomes have become more unequal over the past 20 years, females have become commensurately less likely to commit.
They use statistical tools to show that the effect isn't due to men reacting to changes in female incomes, and it isn't due to women throwing themselves into work when and where male incomes diverge widely.
The finding expressed in numbers: "Increased inequality may account for up to 30 per cent of the overall decline in female marriage rates in the last few decades." And Bush has acted to increase that inequality further. In economic terms he has probably been anti-marriage.
A pro-marriage president or prime minister would use economic and taxation policy to make already successful men less financially attractive, rather than more so.
The very clear implication of the economists' work is that women are materialistic in their approach to marriage.
But that doesn't make me feel bad about women. Economists have shown that all sorts of decisions we make are based on prices, everything from wage rates to exchange rates - among those decisions: how long we sleep each night and where we choose to take our holidays. But much of the time we don't consciously think in those terms.
I prefer to think that women considering marriage don't realise what they are doing.