| Value | Category | Cases | |
|---|---|---|---|
| 1980 | 2 |
1%
|
|
| 1997 | 1 |
0.5%
|
|
| 1999 | 3 |
1.5%
|
|
| 2000 | 2 |
1%
|
|
| 2001 | 2 |
1%
|
|
| 2002 | 6 |
3%
|
|
| 2003 | 11 |
5.5%
|
|
| 2004 | 18 |
9%
|
|
| 2005 | 8 |
4%
|
|
| 2006 | 9 |
4.5%
|
|
| 2007 | 11 |
5.5%
|
|
| 2008 | 9 |
4.5%
|
|
| 2009 | 12 |
6%
|
|
| 2010 | 9 |
4.5%
|
|
| 2011 | 3 |
1.5%
|
|
| 2012 | 9 |
4.5%
|
|
| 2013 | 12 |
6%
|
|
| 2014 | 7 |
3.5%
|
|
| 2015 | 4 |
2%
|
|
| Missing value | 61 |
30.7%
|