Year	Percent
1965	19.0467
1966	21.043
1967	21.21053
1968	20.93461
1969	22.13526
1970	21.99576
1971	24.1035
1972	25.34895
1973	26.0575
1974	35.36633
1975	31.04399
1976	29.08432
1977	29.58164
1978	30.9634
1979	38.98015
1980	40.23725
1981	41.37194
1982	36.90992
1983	34.36425
1984	32.9627
1985	32.10322
1986	30.18267
1987	34.82633
1988	42.01787
1989	44.34561
1990	43.55705
1991	40.36562
1992	39.53509
1993	40.44534
1994	44.93227
1995	44.90435
1996	42.10938
1997	39.11408
1998	38.51979
1999	37.97904
2000	39.5467
2001	42.81669
2002	40.78459
2003	39.48345
2004	42.22114
2005	44.93229
2006	46.02701
2007	51.08611
2008	56.1743
2009	45.83365
2010	50.47808
2011	49.33868
2012	49.39606
2013	47.74453
2014	45.58423
2015	40.6581
2016	40.38877
2017	43.80648