Year	number
2005	34.558282208588956
2006	33.94011976047904
2007	33.247058823529414
2008	32.09356725146199
2009	31.808139534883722
2010	31.174418604651162
2011	29.862068965517242
2012	27.910112359550563
2013	27.414391534391534
2014	26.546666666666667
2015	25.932910052910053
2016	24.95407407407407
2017	23.96904761904762
2018	23.842894736842105
2019	23.121842105263156