Year	Overall average
2004	69.0187591197691
2005	70.894632049062
2006	70.2848861538462
2007	71.1110826495727
2008	71.1965525641026
2009	70.9845006469761
2010	71.3712800562588
2011	71.9690576371308
2012	70.5277777361111
2013	69.6982167352538
2014	70.7009602194787
2015	71.4814897119342
2016	71.8792909465021
2017	71.8930057613169
2018	72.7160543209877