Year	number
2004	6.4375
2005	6.411764705882353
2006	6.411764705882353
2007	6.315789473684211
2008	6.315789473684211
2009	6.105263157894737
2010	6.105263157894737
2011	6.15
2012	6.15
2013	6.15
2014	6.1
2015	5.8
2016	5.8
2017	5.75
2018	5.75
2019	5.4