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The number of on-demand workers in the U.S. is expected to nearly double in the next four years. That means 9.2 million Americans are expected to work in the gig economy by 2021, up from 3.8 million last year, according to combined research by Intuit and Emergent Research.

The rise in on-demand workers has been fueled largely by startups like Uber, TaskRabbit and Airbnb. It has also helped companies like Intuit, which makes tax software QuickBooks and TurboTax. The company’s stock surged to an all-time high yesterday thanks to the gig economy.

For context, there are currently more gig workers than people employed in the entire information sector (which includes publishing, telecommunication and data processing jobs) and IT services combined, according to data from the Bureau of Labor Statistics.

In 2021, the number of on-demand jobs will surpass the current number of jobs in finance (8.4 million) or construction (6.8 million).

The BLS Current Employment Statistics survey doesn’t include numbers for self-employed workers or independent contractors, so the gig economy’s growth is happening outside regular employment metrics.

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