Year	Percent
1970	25.92694
1971	25.93697
1972	25.93455
1973	25.91624
1974	25.89201
1975	25.95494
1976	25.98713
1977	25.92241
1978	25.82473
1979	25.77084
1980	26.26957
1981	26.14813
1982	25.59878
1983	25.33633
1984	25.50139
1985	28.7632
1986	25.54093
1987	22.85207
1988	24.02404
1989	26.32671
1990	24.80249
1991	13.99548
1992	6.54496
1993	6.39438
1994	5.24213
1995	7.01427
1996	15.897
1997	14.95297
1998	13.20313
1999	11.85632
2000	12.50499
2001	11.46472
2002	9.19635
2003	8.50362
2004	8.80062
2005	10.77459
2006	11.72862
2007	10.18277
2008	14.84468
2009	10.9375
2010	10.07337
2011	8.47079
2012	8.57522
2013	9.39363
2014	7.61133
2015	9.37259