I've never been impressed by those economists who think they can use their little pocket model of the economy to explain every aspect of life. Who want to understand the search for a partner by thinking of marriage as a market. Who think the only motivation – the only emotion – is the desire to make a buck.
On the other hand, if economics is, as one great economist said, the study of the daily business of life, if none of us could exist without the wherewithal to pay for food, clothing, shelter and much else, if most of us have to work to earn that wherewithal, and if most of our time is devoted to producing and consuming, then it's hardly likely that big changes in the economy and education and technology have no effect on such things as marriage.
(While I'm on the topic, I'm never impressed by people who profess to have a soul above such a venal and boring subject as economics. Just threaten to cut their income and see if they're still so uninterested.)
So I thought it worth explaining the theories of two academic economists, Betsey Stevenson and Justin Wolfers. Wolfers is the young Sydney economist, long resident in America, who's most likely to make a name for himself in international economics circles. Already has, really.
Wolfers has taken time off from his job as a professor at the University of Michigan while his partner, Stevenson, is working in Washington as an adviser to President Obama.
Their theory is that economic and social changes have caused the basic rationale for marriage to change from "productive" to "hedonic".
Historically, marriage has been the product of the economic environment of the time. People have used marriage and family to overcome the limitations of the formal economy at the time. Social institutions such as marriage have evolved as economic opportunities have changed and the economy's degree of development has risen.
There was a time – I can remember it – when a number of goods and services, such as freshly cooked meals and childcare, weren't sold in the marketplace. And when keeping house involved long hours of labour.
In such circumstances, it made sense for the family to become the firm producing these household services. It also made sense for the partners to a marriage to increase the efficiency of the "firm" by specialisation.
It was usually the case that husbands, being better educated, were better suited to going out and earning income in the marketplace, while wives had prepared themselves for a life of child-rearing and housekeeping.
Largely unconsciously, young women and men sought out partners they believed would be capable opposite numbers in such a production team.
Then followed, in the lifespan of the Baby Boomers, much technological and social change, all of it with economic implications.
With the invention of a host of "mod cons", housekeeping became a lot less time-consuming and onerous. Cheap imported clothing became available, so people stopped making and repairing their own. More processed foods and takeaways became available.
"While the political emancipation of women is surely a key factor in their movement from the home to the market, deeper economic forces are also at play," Stevenson and Wolfers say.
What came first? The rise of feminism, advances in technology or changes in the economy? Easiest to say they all happened at about the same time and interacted with each other.
Once girls started staying on to the end of school, then going on to uni, things really started to change, in the way partners were selected for marriage and in the things going on in the economy.
With more women wanting to take paid work, the market began supplying things to make that possible: more pre-prepared food, childcare, after-school care, people who mow your lawn, cleaners who can whip through your house in an hour before moving on to the next one.
"While the benefits of one member of a family specialising in the home have fallen, the costs of being such a specialist have risen. Improvements in the technology of birth control have made investing in a wife's human capital a better bet ...
"These greater opportunities also connote a greater opportunity cost for a couple contemplating a stay-at-home spouse," the authors say.
Advances in medicine have yielded rising life expectancy, and the average woman will now spend less than a quarter of her adult life with young children in the household.
By increasing the number of potential years in the labour force, the opportunity cost of women staying out of the labour market to be home with children is higher.
"Rising life expectancy also reduces the centrality of children to married life, as couples now expect to live together for decades after children have left the nest," they say.
With women now better educated than men, we've seen the rise of a human version of "assortative mating": the tendency for people to marry those of the same level of education, even the same occupation.
So what drives modern marriage? "We believe the answer lies in a shift from the family as a forum for shared production, to shared consumption . . .
Modern marriage is about love and companionship. Most things in life are simply better [when] shared with another person.
"We call this new model of sharing our lives 'hedonic marriage'."
