It used to be said that behind every successful man was a woman. They meant, of course, a wife. It was a clumsy way of recognising women's contribution within marriage and the part this sacrifice played in helping husbands advance in their careers.

But as we celebrate International Women's Day, I wonder if it's not time to reverse the saying. Let's, in fact, celebrate the role men are now playing in helping women's rise to the top.

This is not to suggest that the fight for equality has been won. Any glance at the continuing gender pay gap or lack of women in the boardroom or parliament shows how hollow that claim would be.

And while we have seen a transformation in family responsibilities, including more men staying at home to let their wives follow their career, we shouldn't exaggerate the revolution. The numbers remain very small. And where both parents work, it is women who are far more likely to shoulder the greater burden at home. We have a long way to go until the playing field is level.

It is, instead, recognition that the fight to overcome the barriers holding women back is being joined by growing numbers of men. And the quicker we recruit more to the ranks, the faster progress will be.

It has been the case, of course, from before the days of the suffragettes that far-sighted men have championed the cause of women's equality. They did so out of a sense of fairness, natural justice or a belief in the dignity of us all as human beings. But this principled argument is now backed by the economic case which shows the stupidity of discriminating against half the population.

It is now clear that businesses or countries which fish in only half the talent pool are putting themselves at a serious disadvantage. This is not just about numbers but also the qualities that women can bring to decision-making. The recklessness which helped spark the global economic crisis might have been prevented with more women at the top of our banks.

All this explains why a growing chorus of senior business figures and politicians, for example, are pressing for a major increase in women in the boardroom. I have reluctantly come to the view that the evidence shows that only statutory targets will achieve these ambitions at the speed needed. But I don't doubt the genuine desire for change in those countries which prefer the voluntary approach.

Even in those societies - and there are many - with much greater barriers to equality than in the UK, we are seeing an increasing recognition among men of the need to enable women to fulfil their potential. It is easy to see why. Research has shown that women in the developing world re-invest a far larger share of their income in their families than men. It's been estimated that India's growth rate would be almost 1% higher annually if the gender labour gap was as small as in China.

So as well as recognising the achievements of women, let's use International Women's Day to encourage more men across the world to join the fight for true equality. After all, the result if we succeed is not just a better world for women but a better world for everyone. And that really is a goal worth celebrating.

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