| Value | Category | Cases | |
|---|---|---|---|
| 1 | ONLY ONCE | 20369 | 
                                    
                                    97.8%
                                 | 
| 2 | MORE THAN ONCE | 451 | 
                                    
                                    2.2%
                                 | 
| 9 | NO RESPONSE | 2 | 
                                    
                                    0%
                                 | 
| Sysmiss | 10238 |