Year	%
1970	60.4108
1971	67.80497
1972	77.73854
1973	77.68464
1974	78.33804
1992	89.49383
1993	88.39325
1994	89.21782
1995	89.60145
1996	89.91499
1997	90.66219
1998	91.71286
1999	92.31058
2000	92.59941
2001	93.68564
2002	93.4632
2003	93.16094
2004	93.22519
2005	93.29179
2006	93.72095
2007	93.61695
2008	94.08083
2009	93.83496
2010	93.78174
2011	93.56083
2012	93.75494
2013	93.91361
2014	93.83915
2015	93.82945
2016	93.81386
2017	93.94921