Year	Percent
1965	30.87649
1966	29.69035
1967	33.33333
1968	40
1969	32.80212
1970	34.83146
1971	34.52869
1972	29.69858
1973	30.77922
1974	31.06904
1975	25.79737
1976	26.58228
1977	26.47504
1978	24.98312
1979	26.80888
1980	40.48902
1981	40.00799
1982	40.34607
1983	44.44804
1984	41.79575
1985	43.76324
1986	41.40115
1987	39.89742
1988	36.66179
1989	34.85064
1990	39.64365
1991	39.84468
1992	42.02237
1993	41.32754
1994	37.88231
1995	36.08174
1996	35.91767
1997	35.15992
1998	34.95783
1999	35.09826
2000	45.55754
2001	45.12386
2002	44.44709
2003	45.93398
2004	47.51217
2005	46.5703
2006	46.93214
2007	47.0545
2008	48.48949
2009	48.56315
2010	49.55258
2011	50.15467
2012	47.71316
2013	48.95016
2014	49.8026
2015	49.74691
2016	50.95108