Year	Percent
1986	11.5457
1987	9.602
1988	8.3374
1989	7.3475
1990	6.4765
1991	5.616
1992	4.7587
1993	6.2657
1994	7.767
1995	7.782
1996	8.4399
1997	7.494
1998	5.6939
1999	5.0645
2000	4.7349
2001	4.9486
2002	5.3108
2003	7.2531
2004	7.1773
2005	8.6326
2006	8.9047
2007	9.4902
2008	8.75
2009	10.0918
2010	11.8633
2011	13.0432
2012	15.4974
2013	16.3675
2014	14.3261
2015	12.7465
2016	11.1662
2017	9.3483