Year	%
1973	73.10134
1974	75.44142
1975	79.68451
1976	76.1948
1977	78.93742
1978	71.81377
1979	78.47659
1980	79.6425
1981	80.18667
1982	82.25436
1983	83.47927
1984	83.60054
1985	86.31431
1986	85.16349
1987	85.65836
1988	86.87633
1989	88.45523
1990	87.32833
1991	90.06432
1992	90.06332
1993	90.46876
1994	90.35073
1995	90.09391
1996	90.08513
1997	89.88864
1998	89.69742
1999	90.6395
2000	90.20273
2001	91.83463
2002	93.59917
2003	93.21499
2004	92.32571
2005	91.1653
2006	91.52678
2007	91.79961
2008	92.32282
2009	91.75399
2010	91.54211
2011	90.94297
2012	87.16232
2013	87.95685
2014	88.7838
2015	90.14256
2016	91.98925
2017	92.5388