Year	Overall average
2004	54.054053963964
2005	55.3153153153153
2006	55.7894735964912
2007	55.9649121929825
2008	55.2046783333333
2009	56.1111113157895
2010	57.8654972807018
2011	57.9532164035088
2012	58.4502922807018
2013	59.045584045584
2014	59.6723646723647
2015	60.5128358974359
2016	59.202294017094
2017	59.5441666666667
2018	62.2507222222222