| Value | Category | Cases | |
|---|---|---|---|
| 1 | Annual | 318 | 
                                    
                                    32.1%
                                 | 
| 2 | Every 2 years | 119 | 
                                    
                                    12%
                                 | 
| 3 | Every 3 years | 442 | 
                                    
                                    44.6%
                                 | 
| 9 | Other (specify)____ | 112 | 
                                    
                                    11.3%
                                 | 
| Sysmiss | 976 |