Year	Percent
1986	8.5256
1987	6.9965
1988	6.1004
1989	5.7901
1990	5.3749
1991	4.7744
1992	3.9687
1993	5.1629
1994	6.8435
1995	7.0153
1996	7.3838
1997	6.5387
1998	5.4195
1999	4.7041
2000	4.1787
2001	4.456
2002	4.8645
2003	6.8856
2004	6.8282
2005	8.4405
2006	8.957
2007	9.5354
2008	8.5584
2009	10.0564
2010	12.1443
2011	12.3116
2012	14.7163
2013	15.5909
2014	13.3984
2015	11.5582
2016	10.4047
2017	8.462