Year	years
2003	2.7606060606060603
2004	2.6888888888888887
2005	2.6487179487179486
2006	2.551219512195122
2007	2.506976744186047
2008	2.4840909090909093
2009	2.484090909090909
2010	2.4931818181818186
2011	2.3840909090909097
2012	2.354545454545455
2013	2.346808510638298
2014	2.336170212765958
2015	2.336170212765958
2016	2.3297872340425534
2017	2.3042553191489366
2018	2.3042553191489366
2019	2.3042553191489366