Year	Percent
1965	38.68136
1966	40.11709
1967	42.6362
1968	43.24266
1969	43.42715
1970	48.08365
1971	43.17879
1972	43.43348
1973	44.69503
1974	46.17636
1975	43.27477
1976	40.95408
1977	44.10666
1978	46.39795
1979	48.1756
1980	52.42683
1981	53.18625
1982	49.301
1983	49.78537
1984	51.94584
1985	53.08954
1986	54.81916
1987	54.07697
1988	52.53552
1989	48.03609
1990	55.85445
1991	60.5612
1992	63.32522
1993	61.0569
1994	60.34202
1995	60.82139
1996	60.06179
1997	59.64244
1998	60.14126
1999	61.92478
2000	61.94535
2001	63.56041
2002	53.54885
2003	50.55964
2004	47.83699
2005	48.48615
2006	48.74913
2007	49.50833
2008	50.25519
2009	53.306
2010	51.49518
2011	51.8119
2012	53.65812
2013	53.91909
2014	52.94054
2015	55.8149
2016	55.87481
2017	56.92023