Tomorrow Japan and South Korea will celebrate White Day, an annual event when men are expected to buy a gift for the adored women in their lives. It is a relatively new concept that was commercially created as payback for Valentine's Day. That's because in both countries, 14 February is all about the man.

On Valentine's Day, women are expected to buy all the important male figures in their lives a token gift: not just their partners, but their bosses or older relatives too. If the present is a romantic one, it is known as honmei-choco (chocolate of love). If it is a mark of respect, it is known as giri-choco (chocolate of obligation).

This seems fair enough. Surely it's reasonable for men to be indulged on one day of the year, given the number of times they're expected to produce bouquets of flowers on spec and surprise their woman with perfume or pearls?

But the idea of a woman spoiling a man didn't sit easily with people. In 1978, the National Confectionery Industry Association came up with an idea to solve this anomaly. They started to market white chocolate that men could give to women on 14 March, as compensation for the male-oriented Valentine's Day.

It started with a handful of sweetmakers churning out candy as a simple gift idea. The day captured the public imagination, and is now a fully-fledged, nationally recognised date in the diary - and one where men are obliged to whip out their credit cards. In fact, men are now expected to give gifts worth triple the value of those they received.

What a complication: not only do men have to remember who bought them what, they have to estimate the value and multiply it by three. The temptation for women in Japan must be to buy every man they know some cheap chocolates on Valentine's Day as an investment. A month later, they could happily sit back as their 300% return of flowers, lingerie, jewellery came flooding in.

More seriously, the fact that a cynical commercial event to 'even things out' is now a well-established day on the calendar is symptomatic of the inescapable fact that men are simply expected to give more, financially speaking. Not just in these two east Asian cultures, but all around the world.

For example, the website TopTable looked at British dinner daters and found that 85% of men would sneakily pick up the bill when their date wasn't looking, even if the evening hadn't gone well. Just one third of the women said they would offer to go dutch. A similar Europe-wide study by SABMiller found that 81% of men expect to pay for all the drinks on a first date.

It doesn't seem to be just a wooing factor: men also fork out more in established relationships. The price comparison website MoneySupermarket worked out that this Valentine's Day, the average man spent £48 on his lucky lover, compared to the £22 spent by women.

Then there's the convenient tradition (also started by a company in a bid to boost sales) that the woman receives two to three months' salary worth of diamonds when her beloved proposes. This idea lives on, yet the convention of the bride's family paying for the wedding is gradually dying out.

I hate to support the opposition, so to speak, but it does seems that men are getting a bit of a rough deal at this stage of our transition to a modern, gender-equal world.

The word on the dating scene suggests it's a significantly more expensive game for the blokes. "I'd always offer to pay my way, but I'd actually think it a bit lame if the man didn't get the first meal," says a single 32-year-old advertising executive, who didn't want to give her name for fear of not getting any more free dates.

"I wouldn't feel obliged," says Martin Hansford, a 40-year-old telecoms consultant. "But I probably just would pay. Unless she's one of those girls who insist, and almost argues, that she pays half."

What about married couples? Alexandra Todd-Nelson, a 38-year-old sales director, agrees that men do tend to buy more material gifts over the course of a relationship. "But", she says, "once we go through labour, that says it all, we're worth every penny."

Does she have a point? Some argue that women, being the childbearers, by default put more into a relationship emotionally and physically.

I'm not sure that this requires men to forever try to compensate women. But it was certainly a savvy move by the Japanese confectionery firms. They put chocolate sales through the roof simply by spotting the one occasion when women bought something for their man and got nothing back in return.