| Value | Category | Cases | |
|---|---|---|---|
| 1 | before 1945 | 144 |
3.1%
|
| 2 | 1945-1960 | 622 |
13.4%
|
| 3 | 1961-1980 | 1914 |
41.2%
|
| 4 | 1981-1990 | 1229 |
26.5%
|
| 5 | after 1990 | 735 |
15.8%
|