Year	Percent
1960	9.50005
1961	14.76892
1962	16.9869
1963	16.22267
1964	15.09317
1965	20.3826
1966	24.61705
1967	27.12904
1968	31.3866
1969	31.89242
1970	31.33602
1971	34.99508
1972	38.24862
1973	53.90161
1974	58.07401
1975	56.29643
1976	55.37396
1977	54.51184
1978	53.56609
1979	53.17272
1980	61.255
1981	65.4451
1982	59.27988
1983	58.18826
1984	61.98508
1985	61.25073
1986	57.38415
1987	60.42427
1988	57.12053
1989	50.8537
1990	48.27647
1991	47.09207
1992	45.25253
1993	42.98079
1994	43.53813
1995	46.78341
1996	46.82401
1997	50.36385
1998	60.28062
1999	54.28933
2000	59.24651
2001	54.69203
2002	51.65626
2003	54.75866
2004	62.53368
2005	60.7543
2006	62.74457
2007	64.87472
2008	85.53839
2009	76.12723
2010	81.46154
2011	89.78458
2012	87.29544
2013	82.35385
2014	77.81135
2015	69.66156
2016	63.72741
2017	68.73568