Year	Percent
1986	12.951
1987	10.5632
1988	9.796
1989	10.0835
1990	8.5373
1991	8.574
1992	9.3316
1993	11.7169
1994	13.9443
1995	12.8124
1996	11.2444
1997	10.83
1998	9.5024
1999	8.9995
2000	9.2493
2001	5.6418
2002	5.8386
2003	5.7568
2004	6.2176
2005	5.6922
2006	4.9484
2007	5.0068
2008	6.4532
2009	11.3468
2010	14.4133
2011	15.3779
2012	18.0996
2013	20.2686
2014	20.4072
2015	18.5075
2016	16.8527
2017	14.843