Year	Percent
1976	11.6165
1977	12.9826
1978	13.2942
1979	12.3872
1980	12.1709
1981	11.6969
1982	15.5003
1983	16.3873
1984	15.4142
1985	14.0177
1986	13.1533
1987	11.9481
1988	10.4903
1989	9.5752
1990	11.0289
1991	12.8965
1992	14.4848
1993	14.42
1994	13.6788
1995	13.1842
1996	13.7819
1997	15.2878
1998	13.5983
1999	12.6763
2000	11.393
2001	11.0976
2002	11.7121
2003	11.7988
2004	11.8289
2005	10.5997
2006	10.4133
2007	10.0561
2008	10.1171
2009	12.2568
2010	12.5084
2011	12.3767
2012	12.7382
2013	12.2289
2014	11.9209
2015	11.2627
2016	11.3151
2017	9.9109