Machine learning and Tableau rank among the fastest-growing, in-demand skills in the US online jobs market, according to the third-quarter skills index released today by Upwork of the top 20 hottest skills on its online staffing platform. Data science was the fastest-growing category.

The 20 hottest skills, which all experienced more than 100% year-over-year growth, include:

1. Machine learning
2. Tableau
3. User experience design
4. C++ programming
5. MySQL programming
6. Pardot
7. Social media management
8. Project management professional
9. Swift development
10. Chat support
11. Android development
12. Unity 3D
13. Shopify development
14. Video editing
15. AutoCAD
16. Facebook marketing
17. API development
18. Content writing
19. .NET framework
20. WordPress development

“The freelance workforce is the best indicator of new skill trends,” said Stephane Kasriel, Upwork CEO. “Businesses are turning to freelancers to complete projects requiring skills that aren’t available locally. Freelancers on Upwork know they are responsible for their own career progression and act on this by getting trained and tested on emerging skills earlier than the traditional workforce.”

The Upwork Skills Index calculates growth rates based on freelancer billings through Upwork in the third quarter 2016 versus the same quarter of the prior year.