Year	Overall average
2004	52.3754787356322
2005	54.0996167816092
2006	55.287356091954
2007	55.4406128735632
2008	55.1340995402299
2009	55.7854405747126
2010	57.2796935632184
2011	57.8927203448276
2012	58.6973178160919
2013	58.7222222222222
2014	58.3148148148148
2015	59.3333488888889
2016	58.2963144444444
2017	58.0740844444445
2018	59.2592688888889