Year	Overall average
2004	56.9509043410853
2005	58.2428939534884
2006	58.8630489922481
2007	59.0439275193798
2008	58.2687337984496
2009	58.837209379845
2010	60.310077751938
2011	60.4392765116279
2012	60.3875968992248
2013	59.5925925925926
2014	60.037037037037
2015	61.6049533333333
2016	60.7160651851852
2017	60.6913674074074
2018	62.6419851851852