Year	number
2003	11.862068965517242
2004	11.382352941176471
2005	11.35135135135135
2006	11.131578947368421
2007	10.868421052631579
2008	10.394736842105264
2009	9.868421052631579
2010	9.631578947368421
2011	9.026315789473685
2012	8.736842105263158
2013	8.552631578947368
2014	8.236842105263158
2015	8.179487179487179
2016	7.871794871794871
2017	7.487179487179487
2018	7.3076923076923075
2019	7.256410256410256