Year	number
2005	40.58888888888889
2006	40.472527472527474
2007	40.02197802197802
2008	38.08791208791209
2009	37.68478260869565
2010	36.76086956521739
2011	34.59782608695652
2012	32.42553191489362
2013	31.88941176470588
2014	30.458039215686277
2015	29.59529411764706
2016	27.80117647058824
2017	26.142647058823528
2018	26.201470588235292
2019	24.995588235294115