| Year | Internal researchers in head count | ||||||
|---|---|---|---|---|---|---|---|
| Less than 25 years | 25–34 | 35–44 | 45–54 | 55–64 | 65 years or over | Total | |
| 2005 | 394 | 8 480 | 6 872 | 7 606 | 6 653 | 1 402 | 31 407 |
| 2006 | 442 | 9 349 | 7 425 | 7 582 | 6 624 | 1 364 | 32 786 |
| 2007 | 646 | 9 904 | 7 574 | 7 051 | 6 438 | 1 446 | 33 059 |
| 2008 | 637 | 10 608 | 7 898 | 6 712 | 6 393 | 1 491 | 33 739 |
| 2009 | 887 | 10 935 | 8 766 | 6 739 | 6 365 | 1 575 | 35 267 |
| 2010 | 594 | 11 006 | 9 808 | 6 534 | 6 163 | 1 595 | 35 700 |
| 2011 | 651 | 11 648 | 10 505 | 6 614 | 5 980 | 1 547 | 36 945 |
| 2012 | 632 | 11 636 | 11 064 | 6 506 | 5 663 | 1 518 | 37 019 |
| 2013 | 699 | 11 676 | 12 140 | 6 729 | 5 361 | 1 198 | 37 803 |
| 2014 | 818 | 12 137 | 12 772 | 6 974 | 5 374 | 1 115 | 39 190 |
| 2015 | 775 | 11 962 | 12 398 | 6 875 | 5 294 | 1 114 | 38 418 |
| 2016 | 612 | 12 228 | 12 371 | 7 177 | 5 407 | 1 120 | 38 915 |
| 2017 | 863 | 13 129 | 13 772 | 7 927 | 5 758 | 1 280 | 42 729 |
| 2018 | 1 005 | 14 000 | 14 649 | 8 888 | 5 902 | 1 505 | 45 949 |
| 2019 | 1 133 | 14 810 | 15 023 | 9 755 | 6 024 | 1 631 | 48 376 |