Year	Percent
1976	16.27
1977	13.08
1978	16.3
1979	14.03
1980	10.07
1981	9.96
1982	18.25
1983	14.69
1984	15.9
1986	9.65
1988	7.75
1989	6.04
1990	5.69
1991	5.74
1992	5.32
1993	5.1
1994	6.78
1995	5.25
1996	9.994
1997	9.588
1998	9.341
1999	13.101
2000	12.481
2001	11.931
2002	11.807
2003	12.03
2004	13.013
2005	12.278
2006	11.756
2007	10.883
2008	12.131
2009	13.42
2010	9.9182
2011	8.8703
2012	8.1335
2013	7.1794
2014	7.1255
2015	7.14
2016	7.2664
2017	7.4608