Year	Overall average
2004	64.4654088259958
2005	66.2997693815514
2006	66.2201350155763
2007	66.8639459813084
2008	66.8431774454829
2009	66.9032715534979
2010	67.587428127572
2011	68.1893004012346
2012	67.3802241794088
2013	66.7317317317317
2014	67.3533533533534
2015	68.1982084084084
2016	68.2082162162162
2017	68.1581621621622
2018	69.0790852852853