Year	Percent
1967	16.33426
1968	13.09007
1969	16.47476
1970	22.23628
1971	21.39054
1972	21.37203
1973	29.80395
1974	45.28023
1975	27.6444
1976	25.49238
1977	27.00701
1978	32.54717
1979	31.88941
1980	36.59734
1981	33.72381
1982	35.76372
1983	39.91476
1984	33.33517
1985	30.31183
1986	35.36405
1987	26.40353
1988	33.10219
1989	34.28327
1990	35.83264
1991	36.08489
1992	33.56092
1993	39.45668
1994	44.38368
1995	44.81927
1996	43.33874
1997	48.19982
1998	45.0972
1999	40.55866
2000	45.73259
2001	49.49058
2002	46.32679
2003	46.75237
2004	42.98731
2005	42.34597
2006	48.83856
2007	45.92732
2008	55.74958
2009	41.84203
2010	50.79032
2011	44.12073
2012	49.29937
2013	46.39757
2014	46.5193
2015	49.74813
2016	49.18264
2017	49.41498