Mary Barra as GM boss is a landmark moment

Female car-buyers opened the door for Mary Barra

I sometimes wonder whether women who get to be the first to the top of a traditionally male industry get tired of articles discussing how remarkable it is that a woman has broken through in defence/tech/banking/cars/the Fed.

When the first woman ever is appointed head of one of Detroit's big three automakers, however, it is worth indulging in a moment of celebration. So, with apologies to newly named General Motors CEO Mary Barra, here are a few thoughts on why this appointment is newsworthy.

In 2007 American women broke through the car barrier, not by crashing into fences, but by purchasing more cars than men.

Yes, cars. Not handbags, or fridges, or window shades, but cars. It was a landmark moment in the growing power of women as consumers, and car manufacturers read the numbers and changed the way they did business. They started designing and marketing cars specifically with women in mind, and promoting more women throughout the industry. Now, with the selection of Ms Barra to head General Motors, that transition has taken another important step. We have a woman running the show.

Ms Barra joins Ginni Rometty, the first female head of IBM; Linda Hudson, the first female head of a major defence company; and Janet Yellen, the first female head of the Fed. In some of the most male-dominated sectors of the American economy, we are now seeing women at the top.

When we get a high profile appointment like this, you can look at it two ways.

It's good news, but remember it is only a token - there are still not enough women at the top.

And the argument has legitimacy. After all, only 4% of CEOs in the US are women. The number rises to a pathetic 5% for the UK, and even the global leaders, China and the Philippines, only have 7% of their CEO desks occupied by women.

Or you can say there are not enough but things are changing very fast and the glass ceiling is shattering with unstoppable determination.

I am not a Pollyanna here, but to deny the progress that women are making misses an important social shift. Although our numbers are not growing fast enough at the top, we are making huge strides. Women are better educated than men, increasingly we earn more than they do (one estimate suggests that by 2018 half of all American women will out-earn their spouses) and, yes, all that spending is giving us the power to change the way companies do business.

The story of Mary Barra, who rose through GM in manufacturing, one of the most macho areas of the car industry, is not just the story of one tough woman doing well, it is newsworthy because it is one more indication of a rapidly changing world. And I have a hunch that in a decade, a woman being made head of any industry won't make headlines at all.

That will be the really good news story.