Year	Percent
1965	30.10335
1966	31.38619
1967	24.34488
1968	21.07912
1969	20.15274
1970	20.1538
1971	20.67606
1972	19.67186
1973	21.17043
1974	42.90081
1975	46.6492
1976	39.88615
1977	44.57377
1978	56.99624
1979	31.27768
1980	34.50518
1981	51.57783
1982	47.66265
1983	47.94336
1984	45.38086
1985	42.71602
1986	40.23382
1987	50.79499
1988	82.76303
1989	51.26305
1990	36.83943
1991	31.80098
1992	27.20758
1993	24.30084
1994	26.38831
1995	25.2829
1996	24.51141
1997	21.84185
1998	22.74699
1999	21.58621
2000	19.88646
2001	18.6419
2002	20.84872
2003	24.54976
2004	32.48316
2005	39.42773
2006	40.96246
2007	43.16711
2008	45.82121
2009	35.98605
2010	36.25623
2011	37.89398
2012	35.29671
2013	32.98747
2014	30.64759
2015	25.52555
2016	24.40679
2017	37.06136