Year	%
1971	54.95728
1972	53.55114
1973	52.81847
1974	53.44964
1975	53.89099
1976	52.53109
1977	52.82592
1978	53.48747
1979	53.67274
1980	53.00367
1981	47.91878
1982	48.93254
1983	48.11435
1984	48.62416
1985	49.51524
1986	50.00706
1987	50.803
1988	52.24184
1989	52.50801
1990	52.07265
1991	52.22993
1992	51.5362
1993	51.14365
1994	51.58087
1995	52.29326
1996	53.25907
1997	52.98324
1998	55.44084
1999	55.43002
2000	57.84133
2001	59.69128
2002	62.28633
2003	64.53735
2004	66.35274
2005	67.33525
2006	69.53668
2007	71.764
2008	71.81198
2009	72.63258
2010	73.47966
2011	73.07926
2012	72.93999
2013	73.43284
2014	73.23036
2015	73.68313
2016	72.56336