Year	number
2005	40.20454545454545
2006	39.82222222222222
2007	39.422222222222224
2008	35.68888888888889
2009	34.869565217391305
2010	33.69565217391305
2011	29.82608695652174
2012	25.574468085106382
2013	24.5021568627451
2014	22.953137254901964
2015	21.81588235294118
2016	19.54137254901961
2017	18.639411764705883
2018	19.051176470588235
2019	18.776666666666667