The data looks reliable. Especially that it mostly overlap with other similar stats like this one:

# Language | Popularity | Avg. Salary global

----------------+------------+------------

1. Javascript | 30.13% | $60,186

2. Java | 27.5% | $61,741

3. Python | 15.58% | $66,353

4. C# | 12.8% | $66,470

5. SQL | 10.97% | $54,139

6. C++ | 9.95% | $69,092

7. Php | 8.74% | $53,420

8. Node.js | 8.45% | $64,818

9. C | 6.28% | $67,720

10.Ruby | 5.08% | $68,478

More stats and details https://jobsquery.it/stats/language/group