Year	number
2003	11.857142857142858
2004	11.3125
2005	11.058823529411764
2006	11.058823529411764
2007	10.210526315789474
2008	9.368421052631579
2009	9.052631578947368
2010	9.157894736842104
2011	9.05
2012	9.047619047619047
2013	8.80952380952381
2014	8.714285714285714
2015	8.571428571428571
2016	8.238095238095237
2017	7.761904761904762
2018	7.142857142857143
2019	6.285714285714286