| Value | Category | Cases | |
|---|---|---|---|
| 1996 | 217 | 
                                    
                                    10.9%
                                 | |
| 1997 | 299 | 
                                    
                                    15%
                                 | |
| 1998 | 383 | 
                                    
                                    19.2%
                                 | |
| 1999 | 538 | 
                                    
                                    27%
                                 | |
| 2000 | 552 | 
                                    
                                    27.7%
                                 | |
| 9997 | inconsistent | 2 | 
                                    
                                    0.1%
                                 | 
| 9998 | dk | 0 | 
                                    
                                    0%
                                 | 
| Sysmiss | 12955 |