Year	number
2003	8.227272727272727
2004	7.956521739130435
2005	7.98
2006	8
2007	7.836363636363636
2008	7.375
2009	7.089285714285714
2010	7.017857142857143
2011	6.724137931034483
2012	6.728813559322034
2013	6.506451612903225
2014	6.333870967741936
2015	6.075806451612903
2016	5.903225806451613
2017	5.709677419354839
2018	5.682539682539683
2019	5.380952380952381