Year	Overall average
2004	53.6111111111111
2005	54.629629537037
2006	55.5864196296296
2007	56.2962961111111
2008	55.5555556481482
2009	57.006172962963
2010	58.8271606481482
2011	59.1049382407407
2012	59.0123455555556
2013	59.9691358024691
2014	59.537037037037
2015	61.0493981481482
2016	61.0493990740741
2017	60.709887037037
2018	62.6851972222222