Year	number
2005	16.104938271604937
2006	16.102409638554217
2007	16.100591715976332
2008	15.735294117647058
2009	15.56140350877193
2010	15.532163742690058
2011	15.377906976744185
2012	15.365714285714287
2013	15.404756756756752
2014	15.474623655913975
2015	15.394216216216213
2016	15.40016216216216
2017	15.315459459459458
2018	15.058870967741932
2019	14.822956989247308