| 2010 | 2011 | 2012 | 2013 | 2014 | 2015 |
---|---|---|---|---|---|---|
Total group (%) | 28.9 | 34.6 | 34.4 | 36.4 | 37.7 | 42.5 |
 Low educational level (%) | 24.6 | 34.8 | 33.7 | 38.4 | 37.6 | 38.6 |
 Moderate education level (%) | 30.5 | 33.1 | 31.0 | 34.5 | 36.7 | 38.2 |
 High educational level (%) | 30.8 | 37.4 | 41.2 | 38.5 | 39.1 | 50.9 |