Year	Percent
1973	48.51881
1974	47.96139
1975	50.05677
1976	51.6246
1977	52.63081
1978	63.28177
1979	53.46072
1980	51.72594
1981	51.90441
1982	50.95636
1983	51.14775
1984	52.7897
1985	54.20522
1986	54.50799
1987	56.15245
1988	55.81443
1990	56.97853
1991	55.70545
1999	49.49926
2000	50.58943
2003	57.98902
2004	60.03145
2006	52.16893
2007	55.53406
2008	71.80578
2009	71.53803
2010	73.58619
2011	72.63963
2012	76.29272
2014	74.79705
2015	76.22256
2016	75.4213