| Year | Excellent quality (%) | text1 | Sufficient and Good quality (%) | text2 | Poor quality (%) | text3 | Quality classification not possible (%) | Text4 |
|---|---|---|---|---|---|---|---|---|
| 2010 | 74.6 | 74.6 | 17.2 | 17.2 | 1.6 | 1.6 | 6.5 | 6.5 |
| 2011 | 78.1 | 78.1 | 14.5 | 14.5 | 1.7 | 1.7 | 5.8 | 5.8 |
| 2012 | 79.1 | 79.1 | 15.1 | 15.1 | 1.8 | 1.8 | 4 | 4 |
| 2013 | 82.6 | 82.6 | 12 | 12 | 2 | 2 | 3.3 | 3.3 |
| 2014 | 83.3 | 83.3 | 11.9 | 11.9 | 1.9 | 1.9 | 3 | 3 |
| 2015 | 84.4 | 84.4 | 11.7 | 11.7 | 1.6 | 1.6 | 2.3 | 2.3 |