Year	Overall average
2004	75.7671958201058
2005	79.1533332275132
2006	79.2062961904762
2007	79.8411641269841
2008	81.1110052380952
2009	81.1639151322751
2010	80.8993652910053
2011	81.2698415873016
2012	81.2698410582011
2013	78.8383838383838
2014	78.3383838383838
2015	77.7777863636364
2016	77.9293
2017	79.0404106060606
2018	78.0555621212121