| Number | 2016 | 2017 | 2018 |
| 1 | 18 (20.00%) | 533 (15.40%) | 526 (14.80%) |
| 2 | 22 (24.45%) | 2212 (63.91%) | 2280 (64.17%) |
| 3 | 36 (40.00%) | 623 (18.00%) | 640 (18.01%) |
| 4 | 12 (13.33%) | 76 (2.20%) | 98 (2.76%) |
| 5 | 2 (2.22%) | 13 (0.38%) | 8 (0.23%) |
| 6 | 0 | 4 (0.11%) | 1 (0.03%) |
| Total firms | 90 (100%) | 3461 (100%) | 3553 (100%) |