This chart strikes me as being incredibly misleading.
In theory, it illustrates the number of women employed in each major industry and what those women are being paid in relation to their male counterparts. But does it take into account job level or differentiation? It’s not clear to me that it does. The financial sector employs a lot of female assistants, which would account for the high female employment/high gender gap of that bubble. The construction industry, on the other hand, has less job differentiation–which is why the average woman is paid nearly the same as the average man.
What does job differentiation have to do with it? In an industry that employs people of vastly different skill sets and educational backgrounds, some jobs will be open to people who are returning to the workforce after a period of not working. For obvious (biological/familial) reasons, those lower-paying jobs are more likely to be filled by women—who will thus drag down the average female pay for that industry.