| Value | Category | Cases | |
|---|---|---|---|
| 1972 | 59 | 
                                                                 
                                    
                                    3.5%
                                 
                                                             | 
                                                        
                    |
| 1973 | 22 | 
                                                                 
                                    
                                    1.3%
                                 
                                                             | 
                                                        
                    |
| 1974 | 37 | 
                                                                 
                                    
                                    2.2%
                                 
                                                             | 
                                                        
                    |
| 1975 | 32 | 
                                                                 
                                    
                                    1.9%
                                 
                                                             | 
                                                        
                    |
| 1976 | 23 | 
                                                                 
                                    
                                    1.3%
                                 
                                                             | 
                                                        
                    |
| 1977 | 44 | 
                                                                 
                                    
                                    2.6%
                                 
                                                             | 
                                                        
                    |
| 1978 | 61 | 
                                                                 
                                    
                                    3.6%
                                 
                                                             | 
                                                        
                    |
| 1979 | 53 | 
                                                                 
                                    
                                    3.1%
                                 
                                                             | 
                                                        
                    |
| 1980 | 69 | 
                                                                 
                                    
                                    4%
                                 
                                                             | 
                                                        
                    |
| 1981 | 65 | 
                                                                 
                                    
                                    3.8%
                                 
                                                             | 
                                                        
                    |
| 1982 | 111 | 
                                                                 
                                    
                                    6.5%
                                 
                                                             | 
                                                        
                    |
| 1983 | 137 | 
                                                                 
                                    
                                    8%
                                 
                                                             | 
                                                        
                    |
| 1984 | 158 | 
                                                                 
                                    
                                    9.2%
                                 
                                                             | 
                                                        
                    |
| 1985 | 175 | 
                                                                 
                                    
                                    10.2%
                                 
                                                             | 
                                                        
                    |
| 1986 | 204 | 
                                                                 
                                    
                                    11.9%
                                 
                                                             | 
                                                        
                    |
| 1987 | 460 | 
                                                                 
                                    
                                    26.9%
                                 
                                                             |