The independent workforce continues to grow and mature, even as the economy continues to rebound and the unemployment rate declines, according to MBO Partners, the nation’s largest provider of business services and tools to the self-employed and companies that engage them. The company released its 2017 State of Independence in America report, the country’s longest-running end-to-end survey of the American independent workforce.

According to the new report, the total number of self-employed Americans aged 21 and above rose to 40.9 million in 2017, up 2.8% from 2016. Independents, who now represent about 31% of the U.S. civilian labor force, are distributed across every demographic, age, gender, skill and income group.

Over 40% of the U.S. adult workforce reports either currently working or having worked as an independent at one time during their careers. Over the next five years, MBO Partners projects that fully half of the U.S. adult workforce will have experienced what independent work can offer.

Independents work in all segments of the U.S. workforce and are of vital impact to our economy, generating roughly $1.2 trillion of revenue for the U.S. economy, equal to about 6% of U.S. GDP.

Three key trends emerged from this year’s study:

• The number of high earning independents rose for the sixth year in a row. Ongoing economic expansion enables those whose skills are in high demand to get more work and to command a premium for their services. Now, 3.2 million full-time independents make more than $100,000 annually, up 4.9% from 2016 and an annualized increase of more than 3% each year since 2011.

• More Americans are seeking to supplement their income with part-time independent work or “side gigging.”Though the economy is getting stronger, the typical American worker has seen very little – if any – wage gains. As a result, many Americans who are struggling to keep up with inflation and higher costs are supplementing their income with part-time independent work or side gigging. Fueled in part by the growth of the increasing number of online platforms, the number of people working as occasional independents (those working irregularly or sporadically as independents but at least once per month) soared 23% to 12.9 million, up from 10.5 million in 2016.

• A strong job market has created a “barbell effect” on both sides of the independent work spectrum. Work opportunities are growing on both sides of the spectrum – both unskilled and skilled – creating a barbell effect. At the low end of the market, there is growing demand for online platform workers, such as Uber drivers or TaskRabbiters, who usually go independent to supplement income, learn new skills or even to socialize in retirement. On the other end of the spectrum, we see a strong rise in entrepreneurial independent professionals earning significant incomes by offering unique services in areas such as technology and marketing.