Year	%
1972	53.11111
1973	49.8875
1975	48.27058
1976	50.49503
1977	51.1672
1978	57.25918
1979	58.2781
1980	58.62769
1982	51.59113
1983	48.56312
1984	54.46426
1985	51.16145
1986	48.12412
1987	49.44451
1993	69.02335
1995	71.02583
1996	68.52887
1997	63.60061
1999	69.07233
2000	70.55824
2006	71.84271
2008	70.04196
2011	77.28643
2013	90.3775
2014	94.4113
2015	94.12181
2016	91.49627