Year	number
2005	40.07142857142857
2006	39.824561403508774
2007	39.48245614035088
2008	37.91228070175438
2009	37.573913043478264
2010	36.84347826086957
2011	35.00869565217391
2012	33.21186440677966
2013	32.775555555555556
2014	31.704126984126987
2015	31.029523809523813
2016	29.60888888888889
2017	28.107539682539684
2018	28.147222222222222
2019	27.171031746031748