Welcome to the "gig" economy, where workers swap payroll jobs for self-directed hustle. Behind the shift: a desire for income and financial security that can elude workers tethered to one employer, a quest for more freedom and flexibility when it comes to work hours and location and the old-fashioned itch to start a business.

Some 54 million to 86 million people in the U.S. are independent workers, according to McKinsey Global Institute’s study, "Independent Work: Choice, Necessity, and the Gig Economy," released in 2016. They account for 20 percent to 30 percent of the working-age population in the U.S. and five European countries included in the report.

Defined as working with a high level of control and autonomy, payment by task, assignment, or sales, and a short-term relationship between worker and client, the independent segment is growing and is much bigger than official estimates, McKinsey says.

"A full-time job with one employer has been considered the norm for decades, but increasingly, this fails to capture how a large share of the workplace makes a living," the report said.

Today, some 3.9 million people work on-demand jobs that they find via digital marketplaces, such as Lyft and Upwork. Some 41 percent of them also hold down fulltime jobs and most, 67 percent, are satisfied with their on-demand work. The ranks of these on-demand workers will grow to 7.7 million by 2020, according to a new study by Intuit and Emergent Research.

 "We’re continuing to see how profoundly the on-demand economy and technology is reshaping the American workforce and overall economy," Dan Wernikoff, executive vice president and general manager for Intuit TurboTax, the financial-software company that serves entrepreneurs, said in a release. "More people are using on-demand work to improve their financial stability."

 "Dispatches from the New Economy: The On-Demand Workforce, is based on an online survey of 6,247 independent workers who find work opportunities via one or more of 12 online platforms.

"I decided to start working on a platform while I was an attorney at a law firm that told me there might not be enough work to justify my role," said  Josh Garber, a startup attorney in San Francisco cited in the Intuit study who now finds his legal clients online via UpCounsel. "I wanted to know that I could have financial security if I was let go, and also to see if I could successfully run my own business."

Garber’s firm is now his full-time job. "My lifestyle has changed dramatically," he said. "I have the ability to create my own schedule, to focus on eating right and my physical/mental health, to travel and work from anywhere and to avoid the stress of a commute and office politics."

He’s not alone. "There are many experienced workers who choose to have the flexibility," said Arun Srinivasan, senior vice president at SAP Fieldglass. "It’s not like they’re compromising on their lifestyle or earnings. They have found a different way to engage with different companies.

"When they are highly skilled, they are saying, ‘Why should I be engaged with one employer?’"

Among the reasons even a happily employed fulltime worker might want to explore gig work:

• To protect your livelihood. Depending on one employer for continued fulltime employment may be risky. Manufacturing jobs go to robots. Startups fold. Once-dominant businesses are violently reshaped by technological change. When companies shrink to wring out costs, senior full-timers are likely first on the firing line. Developing an alternate, flexible income stream is a form of insurance.

• To overcome a near-term financial setback. The gig economy is a smart way to generate additional income, said Cassie Divine, vice president, QuickBooks Self-Employed. One in five of the on-demand workers polled in the Intuit study had experienced a financial hardship – such as a job loss, cut in work hours or unexpected major expense. "They turned to on-demand work as an easy way to overcome it," she said.

• To diversify and add to your professional skill set. "Freelance work can be a great way to monetize a talent or skill in addition to what you’re already doing," said Brent Messenger, head of global community for Fiverr.com, an online marketplace. Working solo can broaden your expertise as a problem solver, serving customers from concept to delivery.

Technology makes it easy to try. There are online marketplaces for a seemingly endless list of jobs: Lessonface (live online music lessons), Thumbtack (local services "from house painting to personal training"), Makers Row (business-to-business manufacturing), Amazon Mechanical Turk (global marketplace for on-demand tasks), and Upwork, Freelancer, CrowdSource and Toptal for freelance writers, web designers, marketers, designers and consultants.

Ready to gig? Here are some questions you must answer.

1. What are you really good at? "Identify your passion and learn to market it. Just like with a traditional career, doing something you’re passionate about will ultimately bring the most long-term fulfillment," said Fiverr’s Messenger.

2. How are your networking skills? While you may have networks of colleagues from your industry, think about joining freelance communities to learn about how others are finding success..

3. How can you demonstrate your expertise? Learning to market your services can be a big hurdle. Word of mouth is a good place to start.

4. Is there an online platform for your talent?

"Online freelance marketplaces can be a huge asset, connecting you to millions of buyers who are looking for the types of services you sell," said Messenger. Search for a marketplace that might work for you.

5. Do you have some savings? Build backup savings to help smooth out the inevitable bumps in the road of working independently.