Bureau of Labor Statistics:  The occupations with the largest employment in May 2014 were retail salespersons and cashiers. These two occupations combined made up nearly 6 percent of total U.S. employment, with employment levels of 4.6 million and 3.4 million, respectively. Of the 10 largest occupations, only registered nurses with an annual mean wage of $69,790, had an average wage above the U.S. all-occupations mean of $47,230. The highest paying occupations overall included several physician and dentist occupations, chief executives, nurse anesthetists, and petroleum engineers. Jobs and Wages

Wiomen out number men 10 to 1 in the profession in the US, but still get paid less than male nurses.