| Value | Category | Cases | |
|---|---|---|---|
| 1997 | 1 | 
                                    
                                    2%
                                 | |
| 2003 | 1 | 
                                    
                                    2%
                                 | |
| 2008 | 1 | 
                                    
                                    2%
                                 | |
| 2009 | 1 | 
                                    
                                    2%
                                 | |
| 2010 | 1 | 
                                    
                                    2%
                                 | |
| 2013 | 2 | 
                                    
                                    4.1%
                                 | |
| 2014 | 5 | 
                                    
                                    10.2%
                                 | |
| 2015 | 6 | 
                                    
                                    12.2%
                                 | |
| 2016 | 6 | 
                                    
                                    12.2%
                                 | |
| 2017 | 7 | 
                                    
                                    14.3%
                                 | |
| 2018 | 13 | 
                                    
                                    26.5%
                                 | |
| 2019 | 5 | 
                                    
                                    10.2%
                                 |