| Year | Average | 10th percentile | 90th percentile | Target value |
|---|---|---|---|---|
| 2006 | 18.21 | 11.25 | 29.72 | 25 |
| 2007 | 16.31 | 9.94 | 25.38 | 25 |
| 2008 | 17.67 | 9.66 | 25.06 | 25 |
| 2009 | 17.22 | 11.42 | 24.15 | 25 |
| 2010 | 18.11 | 10.39 | 27.87 | 25 |
| 2011 | 18.99 | 11.75 | 29.21 | 25 |
| 2012 | 17.08 | 10.85 | 26.92 | 25 |
| 2013 | 16.06 | 9.42 | 24.25 | 25 |