Year	number
2003	12.176470588235293
2004	11.6
2005	11.545454545454545
2006	11.173913043478262
2007	10.91304347826087
2008	10.08695652173913
2009	9.217391304347826
2010	8.956521739130435
2011	8.304347826086957
2012	8.375
2013	8.291666666666666
2014	8
2015	8
2016	7.6
2017	7.24
2018	7.12
2019	7.04