By tradition, 29th February is the one day in every four years when a frustrated woman can pop the question to her hesitant or resistant man.
It would be easy to write off this leap day tradition as outdated or sexist. After all, in our enlightened times of male and female equality, it should be as normal for a woman to propose as a man. Shouldn't it?
Before we consign this unfortunate relic of patriarchy to the bin of history, we might consider an important aspect of human nature that hasn't changed. Men commit in a fundamentally different way to women.
Let me start with an anecdote that illustrates this.
'John' and 'Jane' had two young children and had been married for ten years when they came to see me in distress. Seemingly happy as a couple and coping well enough with the pressures of family life, Jane had been devastated to discover John was having an affair. Not wanting to throw away her marriage cheaply, she persuaded John to come with her to try and salvage the situation.
I started by asking them to tell their story, one at a time. Jane went first, telling of how falling in love naturally moved into getting married and having children. They had their share of ups and downs. But their marriage was solid, or so she thought.
John then told his version, of falling in love but not yet sure about a life together. Their discussions about marriage were very much led by Jane. In the end, he felt pressured into proposing. Marriage was "like getting onto a train I couldn't get off." His first six months of married life were filled with turmoil. Jane was open-mouthed in astonishment. She had no idea.
John was a classic 'slider' rather than a 'decider'. He had slid into marriage, rather than decided. Having not fully bought in to the idea of marriage in the first place, it was only a matter of time before an attractive alternative crossed his radar. I told him he had to make that decision pretty quickly. He was lucky to have a wife who was prepared to give him a second chance. His only chance of a happy marriage was to commit properly now.
Researchers describe commitment in terms of sliding, deciding and inertia. Dedication - the interpersonal aspect of commitment - tends to be lower among men in particular who 'slide' rather than 'decide' through relationship transitions. 'Inertia', or 'premature entanglement', then makes these less committed men drift onwards until something dramatic causes them to break free.
Two studies illustrate this nicely.
The first study of 1,400 young unmarried couples asked what factors distinguished between those still together one year later and those not. If they'd either bought a home together, signed a phone contract together, joined a sports club together, or even had a pet together, they tended to do better. Although each of these factors individually predicted greater stability, the effects were cumulative - so the more signs of commitment the better. Remarkably, the two big factors that did not predict future stability at all were living together or having a baby.
The second study looked at commitment among a sample of newlyweds. During their first few years of married life, the couples were asked about their sense of dedication to one another. This was measured by how much they saw themselves as a couple, their sense of future together, how much they prioritised their relationship, and their willingness to sacrifice and to forgive. Even five years in, one group stood out as being significantly less committed than anyone else. Husbands who had lived with their future wife before they got engaged, rather than afterwards, were less committed. This wasn't true for wives. Wives commitment didn't depend at all on whether they moved in before or after getting engaged.
These US findings are pretty remarkable. The first study shows the importance of decision-making in general. Whereas moving in together and having a baby can just kind of happen, few people sign a mortgage or get a pet by accident. Deciding - rather than sliding - is a key characteristic of commitment. The second study shows how decision-making is particularly important for men.
If anything, the UK evidence is even stronger. As part of my work for Marriage Foundation, I produced an analysis of UK divorce rates, which have collapsed in recent years. The knee-jerk explanation is that fewer people are getting married. This is wrong for all sorts of reasons, not least that there are still twice as many weddings as divorces in any year.
But look more closely at where the change has happened. Divorces granted to husbands have barely changed since the 1970s. Yet since 2003, divorces granted to wives during their first three years of marriage have fallen by half and those during the first decade of marriage have fallen by a quarter.
Any explanation has to take account of this very strong gender effect. Falling divorce rates can't simply be down to fewer weddings or couples marrying older because these factors would affect both spouses equally.
The real reason is simple. Fewer wives are filing for divorce because the latest generation of husbands are more committed to marriage in the first place. As social and family pressures to marry have reduced, so those men who marry really mean it.
In short, today there are fewer 'sliders' and more 'deciders' getting married. More committed men means fewer unhappy wives.
When we make a decision about more or less anything, we buy into a plan and become intentional about making it work. This is one of the more plausible explanations for why the act of marriage might make a difference to the couple's stability. Marriage represents the ultimate act of dedication, a decision to be a couple with a permanent future.
There's nothing remotely quaint, or misogynist, or sexist about this tradition that men should do the proposing. It's rooted in human nature and the need for men to buy in. Most of us know this. In a survey we did of cohabiting couples, 32% of the women said they weren't married because they were waiting for him to ask. Only 7% of the men were waiting for her to ask.
So if you are a frustrated woman who is desperate to make an honest man of him, beware that you don't end up like poor Jane.
Your man needs to make the decision for himself. Even if he says yes, he still might not have bought in.