Millions of people are planning to quit their corporate jobs and work for themselves over the next few years, according to a new survey by Freshbooks, the cloud-based accounting software firm.

The survey of 2,700 full-time employees, conducted at the end of 2017 in cooperation with Research Now, shows the number of Americans who plan to work for themselves could triple to as many as 42 million workers by 2020. That's an increase of 27 million workers who say they are ready to abandon traditional work for full-time self-employment. Of this number, 42 percent are expected to be Millennials. 

So what's behind this coming exodus of employees from the corporate workforce? Here are the top reasons respondents gave for wanting to quit the 9-to-5:

  • 43 percent say they want more control over their career
  • 43 percent say they want to make a career change
  • 33 percent want to leave for financial reasons
  • 32 percent want to leave for family reasons
  • 15 percent want to leave for health reasons

Of course, most people can't just leave their 9-to-5 jobs whenever they want to. Here are seven ways Millennials and other respondents are preparing for the day they turn-in their corporate badge and walk free of their cubicle farm:

  • 58 percent are saving money or paying off debt
  • 52 percent are learning new skills
  • 45 percent are reaching out to potential clients
  • 42 percent are taking advice from other entrepreneurs
  • 36 percent are building their personal brand online
  • 26 percent are taking courses in-person or online
  • 26 percent are lining up investors or partners

But are people really happy once they've struck out on their own? Apparently they are, according to the survey. Overall, self-employed professionals enjoy greater career satisfaction than those with traditional jobs: 71 percent versus 61 percent holding down a traditional role at a company. 

And this satisfaction gap widens further as workers age, with the gap reaching as much as 30 percent between the self-employed cohort and the traditionally employed cohort. Apparently, the combination of a better work-life balance, improved health, and more income makes life as an independent professional all the more attractive over time. 

And once they've left the 9-to-5, people don't want to go back: 97 percent of professionals who are currently self-employed said they have no plans to return to a corporate job.