Year	number
2003	8.121212121212121
2004	7.4411764705882355
2005	7.411764705882353
2006	7.2
2007	7.114285714285714
2008	6.628571428571429
2009	6.3428571428571425
2010	6.285714285714286
2011	6.0285714285714285
2012	6.0285714285714285
2013	5.7631578947368425
2014	5.605263157894737
2015	5.473684210526316
2016	5.363947368421052
2017	5.337631578947368
2018	5.337631578947368
2019	5.206052631578947