Pew Research Center finds that working mothers are the sole or primary provider in four out of 10 U.S. households with children under the age of 18. There has been a significant increase in mothers who are the head of their households. Roughly 40% of working mothers make up this group today, compared with 11% back in 1960. Take a look at this infographic by Mint.com to get a visual representation of the financial lives of working mothers.