| Year | Average | 10th percentile | 90th percentile | Limit value | Target value |
|---|---|---|---|---|---|
| 2006 | 18.2 | 11.2 | 31.4 | 25 | |
| 2007 | 16.6 | 9.9 | 25.6 | 25 | |
| 2008 | 17.7 | 9.6 | 25.5 | 25 | |
| 2009 | 17.2 | 11.3 | 24.4 | 25 | |
| 2010 | 18.1 | 10.3 | 27.9 | 25 | |
| 2011 | 19 | 11.7 | 30 | 25 | |
| 2012 | 17.2 | 10.8 | 27.3 | 25 | |
| 2013 | 16.2 | 9.6 | 23.8 | 25 | |
| 2014 | 15.2 | 9.4 | 23.9 | 25 | |
| 2015 | 14.7 | 9.0 | 24 | 25 | |
| 2016 | 14.2 | 8.5 | 23.3 | 25 |