Year	Overall average
2004	55.5820104761905
2005	56.4021163492064
2006	56.9047617460317
2007	57.116401984127
2008	56.2169311904762
2009	57.1693122222222
2010	58.835978968254
2011	59.6031744444444
2012	59.1731265116279
2013	58.75
2014	58.1186868686869
2015	59.4949613636364
2016	59.5454659090909
2017	59.7979856060606
2018	61.7171795454546