The number of self-employed Americans has been on the decline since 2006. Although a small increase occurred between 2012 and 2013, Economic Modeling Specialists International, a unit of CareerBuilder, says something is definitely going on that’s cutting into the numbers of those who work for themselves.

The study produced by EMSI contains loads of data, with the self-employed sliced and diced in multiple ways.

In general, EMSI tells us, about 10 million Americans, or 6.6 of its workers, are self-described solo flyers. At the height of the self-employment craze in 2006, the percent was 7.2.

The biggest percentage declines hammered:

  • Construction managers: -38 percent
  • Construction supervisors: -33 percent
  • Real estate agents: -22 percent
  • Farmers and ranchers: -22 percent
  • Non-retail sales supervisors: -21 percent
  • Retail supervisors: -19 percent
  • Dentists: -19 percent
  • Personal financial advisors: -17 percent

Which occupations experienced growth? The leaders:

  • Medical transcriptionists: 375 percent (that is not an error)
  • Web developers: 67 percent
  • Recreation workers: 40 percent
  • Home health aides: 22 percent
  • Personal care aides: 18 percent

What EMSI doesn’t really try to do in the narrative with its survey is explain two phenomena: Why the numbers of self-employed exploded between 2001 and 2006 (increase: 1.7 million), and why the numbers have generally declined (decrease: 930,000) since.

“Economic forces like the credit crisis and housing bubble either soured people on self-employment or made it harder for them to start and sustain their own businesses,” the researchers said.

The decline in self-employed jobs coincides with a rise in Americans working on the side to supplement their incomes. More people are getting second and third jobs, but fewer people are dropping their day jobs altogether to work on their own. According to a new CareerBuilder survey, 20 percent of full-time workers picked up a second job in 2013 or plan to do so in 2014.