Year	number
2003	8.588235294117647
2004	8.176470588235293
2005	8.176470588235293
2006	7.611111111111111
2007	7.388888888888889
2008	6.7894736842105265
2009	6.631578947368421
2010	6.526315789473684
2011	6.45
2012	6.5
2013	6.1
2014	5.8
2015	5.65
2016	5.5
2017	5.4
2018	5.45
2019	5.15