Year	Percent
1983	27.02
1984	29.18
1986	18.9
1988	18.01
1989	15.32
1990	12.44
1991	15.22
1992	13.19
1993	12.13
1994	15.37
1995	12.75
1996	23.705
1997	23.563
1998	23.076
1999	31.994
2000	31.547
2001	29.913
2002	31.051
2003	31.968
2004	31.428
2005	30.547
2006	27.766
2007	26.763
2008	29.56
2009	31.423
2010	21.999
2011	21.3335
2012	19.5527
2013	19.5926
2014	20.125
2015	18.773
2016	17.9599
2017	18.7689