Year	number
2003	10.447368421052632
2004	10.24390243902439
2005	10.391304347826088
2006	10.391304347826088
2007	10.152173913043478
2008	9.73913043478261
2009	9.5
2010	9.282608695652174
2011	8.934782608695652
2012	8.872340425531915
2013	8.841764705882353
2014	8.654901960784313
2015	8.419607843137255
2016	8.24313725490196
2017	8.037843137254901
2018	7.6168627450980395
2019	7.196078431372549