Year	number
2003	11.928571428571429
2004	11.5
2005	11.235294117647058
2006	11.235294117647058
2007	10.368421052631579
2008	9.526315789473685
2009	9.210526315789474
2010	9.31578947368421
2011	9.2
2012	9.19047619047619
2013	8.952380952380953
2014	8.857142857142858
2015	8.714285714285714
2016	8.380952380952381
2017	7.9523809523809526
2018	7.333333333333333
2019	6.428571428571429