Bitcoin topped online staffing provider Upwork’s fourth-quarter list of the 20 fastest-growing skills in the US freelance job market as the cryptocurrency craze continues. Bitcoin is a cryptocurrency supported by blockchain, a distributed ledger technology.

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

The skills categories on the list in the fourth quarter all experienced more than 120% year-over-year growth; the top 10 grew more than 300%. More than half of the skills, 55%, are new to the list.

The top 20 fastest-growing skills:

1. Bitcoin
2. Amazon DynamoDB
3. React native
4. Robotics
5. Go development
6. Forex trading
7. 3D rigging
8. Augmented reality
9. Computer vision
10. Penetration testing
11. Media buying
12. Chef.io
13. Shopify development
14. AngularJS development
15. Swift development
16. Video editing
17. Influencer marketing
18. Machine learning
19. 3D modeling
20. Motion graphics