Year	Percent
1975	12.87
1977	11.9
1980	11.5
1983	14.22
1984	16.27
1985	18.65
1986	17.16
1987	14.48
1991	13.53
1992	13.01
1993	11
1994	12.3
1995	11.32
1996	14.94
1997	15.1
1998	18.03
1999	23.31
2000	24.47
2001	19.404
2002	20.011
2003	18.645
2004	18.021
2005	15.884
2007	14.812
2008	14.767
2009	15.839
2010	14.1989
2011	13.1028
2012	12.6632
2013	11.6709
2014	11.0277
2015	10.8444
2016	11.2055
2017	11.5126