Year	Percent
1975	11.21
1976	12.93
1978	13.71
1980	18.44
1981	13.8
1982	15.62
1985	18.68
1988	13.17
1990	9.31
1991	9.51
1992	9.4
1993	10.87
1994	9.59
1995	10.83
1996	9.97
1997	10.42
1998	10.02
1999	10.01
2000	10.1675
2001	10.23
2002	9.8451
2003	7.78
2004	8.09
2005	7.6371
2006	7.0127
2007	6.088
2008	7.43
2009	8.5186
2010	9.2086
2011	9.6
2012	10.5089
2013	11.2302
2014	10.0941
2015	9.8988
2016	9.5955
2017	8.4462