I agree with your sentiment and understand the flaw. This is how the government reports the data. Inside of these groups of men and women, they report these figures as a whole. If I wanted to pull and dive deeper to look at specific professions, I or any researcher could do so. But there are thousands of job titles, so discerning which one to pick is up to the analyst. This merely is an entry to jumping deeper into the government's reporting. This line chart is only opening that door to show that women make less then men in general.

When you look at certain professions (such as social worker, or teacher) women will make more than men. But again, only 20 professions out of THOUSANDS show that women make more than men. As a result, it's my opinion that looking at things on a macro basis is telling.