Year	number
2005	15.411764705882353
2006	15.470588235294118
2007	15.529411764705882
2008	15.529411764705882
2009	15.529411764705882
2010	15.470588235294118
2011	15.823529411764707
2012	16.61111111111111
2013	15.877500000000001
2014	15.977500000000001
2015	15.977500000000001
2016	16.0275
2017	16.05
2018	15.517500000000002
2019	15.1