Year	Percent
1960	21.75975
1961	16.93156
1962	15.98571
1963	18.18679
1964	16.41
1965	16.57235
1966	14.49625
1967	20.79589
1968	22.02253
1969	24.75315
1970	28.84137
1971	35.42231
1972	31.21961
1973	30.80785
1974	32.68711
1975	32.50412
1976	34.93319
1977	39.83476
1978	36.42052
1979	30.86074
1980	28.03768
1981	44.68988
1982	38.49253
1983	35.14864
1984	43.28659
1985	50.68314
1986	43.03564
1987	38.97819
1988	49.0049
1989	42.53494
1990	28.21479
1991	28.74492
1992	53.86078
1993	42.00069
1994	51.88114
1995	53.72674
1996	50.07292
1997	48.71486
1998	46.55629
1999	43.53503
2000	39.11744
2001	37.19852
2002	38.39442
2003	36.68785
2004	32.34253
2005	33.22924
2006	38.19243
2007	51.65995
2008	50.0734
2009	46.34175
2010	47.85328
2011	45.28911
2012	46.38285
2013	54.5136
2014	65.88811
2015	51.17145
2016	53.7078
2017	54.45194