Year	number
2003	8.136363636363637
2004	7.869565217391305
2005	7.9
2006	7.903846153846154
2007	7.709090909090909
2008	7.25
2009	6.964285714285714
2010	6.892857142857143
2011	6.603448275862069
2012	6.610169491525424
2013	6.387096774193548
2014	6.225806451612903
2015	5.967741935483871
2016	5.790322580645161
2017	5.596774193548387
2018	5.571428571428571
2019	5.26984126984127