Year	number
2005	14.98
2006	15.25
2007	15.272727272727273
2008	15
2009	14.571428571428571
2010	14.553571428571429
2011	14.482758620689655
2012	14.271186440677965
2013	14.312903225806453
2014	14.254838709677419
2015	14.206451612903225
2016	14.175806451612903
2017	14.12741935483871
2018	13.998412698412698
2019	13.807936507936507