Year	number
2003	12.444444444444445
2004	11.631578947368421
2005	10.428571428571429
2006	10.321428571428571
2007	9.964285714285714
2008	9.857142857142858
2009	9.678571428571429
2010	9.642857142857142
2011	9.275862068965518
2012	9.241379310344827
2013	8.870967741935484
2014	8.741935483870968
2015	8.64516129032258
2016	8.451612903225806
2017	8.387096774193548
2018	8.193548387096774
2019	8.161290322580646