Year	number
2003	11.558823529411764
2004	10.86111111111111
2005	10.522727272727273
2006	10.355555555555556
2007	9.8
2008	9.311111111111112
2009	8.782608695652174
2010	8.652173913043478
2011	8.391304347826088
2012	8.27659574468085
2013	8.106666666666667
2014	8.03156862745098
2015	7.882352941176471
2016	7.66764705882353
2017	7.5696078431372555
2018	7.185098039215688
2019	7.180588235294119