This is Milton Friedman's 98th birthday – or would be, though sadly he is no longer with us to enjoy it.

It's remarkable how the most effective advocates of the free market economy come from poor backgrounds. Perhaps they are best placed to understand the importance of individuals having the freedom to fulfil their own potential and to rise in whatever walk of life they choose. Those born wealthy or into powerful political families hardly need to bother with such things.

In Friedman's case, he was born in Brooklyn, New York, to poor Jewish immigrants. Before he was born, his mother worked as a seamstress in a New York sweatshop. It's a background that you might think would engender a resentment against American capitalism. But not a bit of it. Friedman understood this menial work for what it was – an essential first rung on the income ladder for unskilled workers and for immigrants who inevitably begin by being undervalued by the home community.

That is why he walked straight into the lion's den by taking his Free to Choose television audience to just such a sweatshop in Hong Kong. Far from showing the evils of capitalism, he argued, the first foot on the ladder that it gave workers showed clearly that political attempts to outlaw low wages and disagreeable working conditions help only those already in good and well-paid jobs. But such measures simply deny opportunities to the people who need them most – to unskilled workers, to young and inexperienced people, to immigrants who are often resented, disliked, and untrusted.

Friedman's birthday is one that the world's poor, in particular, should celebrate.