I am honestly curious... where does that income come from? We know it doesn't come from wages, because median wages of the lower 90% have risen less than 2% si

I am honestly curious... where does that income come from? We know it doesn't come from wages, because median wages of the lower 90% have risen less than 2% since 1980. Since the statistic is based on families, is it due to a larger number of 2-income families out of necessity?