Women in the US earn 4.5% of the world's income all by themselves!
It is actually a few hundred girls and boys each year. This is still horrible, but much, much, MUCH smaller than the number more commonly quoted.
This result is the simple average of women's earnings vs men's earnings. It does not account for differences in hours worked per week, occupations, positions, etc.
For more detail, see the full article: http://time.com/3222543/5-feminist-myths-that-will-not-die/