| Value | Category | Cases | |
|---|---|---|---|
| 1981 | 2 | 
                                                                 
                                    
                                    5.3%
                                 
                                                             | 
                                                        
                    |
| 1982 | 3 | 
                                                                 
                                    
                                    7.9%
                                 
                                                             | 
                                                        
                    |
| 1983 | 4 | 
                                                                 
                                    
                                    10.5%
                                 
                                                             | 
                                                        
                    |
| 1984 | 8 | 
                                                                 
                                    
                                    21.1%
                                 
                                                             | 
                                                        
                    |
| 1985 | 4 | 
                                                                 
                                    
                                    10.5%
                                 
                                                             | 
                                                        
                    |
| 1986 | 6 | 
                                                                 
                                    
                                    15.8%
                                 
                                                             | 
                                                        
                    |
| 1987 | 7 | 
                                                                 
                                    
                                    18.4%
                                 
                                                             | 
                                                        
                    |
| 1988 | 4 | 
                                                                 
                                    
                                    10.5%
                                 
                                                             | 
                                                        
                    |
| Sysmiss | 61 |