Gig economy workers represented 31% of all US workers in 2017 — a total of 48 million workers — according to recently released research by Staffing Industry Analysts. That’s up from 29% in SIA’s previous report based on 2015 data. SIA considers contingent and gig to be synonymous.

The report also found $864 billion in US revenue was generated from contingent work, representing growth of 8.8% from 2015.

“The gig economy continues to grow globally, impacting and advancing how work is being facilitated across industries, professions, skill sets and geographies,” SIA President Barry Asin said. “As the US gig economy also continues to grow, platform development and increased awareness and adoption from stakeholders, especially in the human cloud segment of the gig economy, are driving innovation and access to talent.”

SIA’s definition of “gig economy” is broad and includes temporary agency workers, other temporary workers, independent contractors, statement-of-work consultants and human cloud workers. The last category, human cloud, refers to workers who operate through online platforms such as Upwork, Freelancer.com or online work services platforms such as Uber or Lyft.

The number of human cloud workers is estimated at 13.5 million, which is different from the estimate released by the US Bureau of Labor Statistics. However, a previous release of the bureau’s numbers had raised eyebrows as being inconsistent with other measures.

SIA estimated global revenue in the human cloud at $82 billion in 2017.

The five largest B2B human cloud firms with 2017 revenue:

1. Upwork, $1.36 billion
2. MBO Partners, $525 million
3. Gerson Lehrman Group, $320 million
4. Axiom, $250 million
5. WorkMarket, $200 million

Upwork held an initial public offering today.

“Technology is transforming how millions of people — from dishwashers to drivers to nurses to designers to rocket scientists — find and connect to work, which is changing how companies recruit and provide economic opportunity for people around the world in the process,” said David Francis, Research Manager at SIA.

The full report is available to corporate members of SIA. However, a free summary of the report is available publicly online.

Information on the report is being released publicly as SIA gears up for its Collaboration in the Gig Economy conference, set to begin later today in Dallas. The event is expected to draw more than 800 attendees to discuss the latest trends in the gig economy, including the human cloud.