| Value | Category | Cases | |
|---|---|---|---|
| 1949 | 19 | 
                                    
                                    4.8%
                                 | |
| 1950 | 34 | 
                                    
                                    8.5%
                                 | |
| 1960 | 37 | 
                                    
                                    9.3%
                                 | |
| 1970 | 149 | 
                                    
                                    37.4%
                                 | |
| 1980 | 22 | 
                                    
                                    5.5%
                                 | |
| 1990 | 31 | 
                                    
                                    7.8%
                                 | |
| 2000 | 98 | 
                                    
                                    24.6%
                                 | |
| 2010 | 8 | 
                                    
                                    2%
                                 | |
| Sysmiss | 2 |