The article uses the definition that "same rank" == "same work", which is ridiculous for many reasons, one in particular being that title often corresponds to a pay level for an area of work covered by a ladder of such titles so by definition it will be true that such a gap is insignificant.

> According to data for 8.7m employees worldwide gathered by Korn Ferry, a consultancy, women in Britain make just 1% less than men who have the same function and level at the same employer.

It's not ridiculous because the alternative is almost impossible to quantify and calculate

It's easy, just like the income tax. Get into every nook and cranny of how things are done and control absolutely everything.