Year	Percent
1983	10.1507
1984	9.401
1985	9.8974
1986	10.2513
1987	11.3657
1988	10.4721
1989	8.8357
1990	8.6532
1991	9.1366
1992	10.7464
1993	13.022
1994	11.6113
1995	10.1772
1996	9.5519
1997	7.8865
1998	6.8362
1999	6.4092
2000	5.6391
2001	4.3396
2002	4.3299
2003	4.2765
2004	3.8281
2005	3.4033
2006	3.5242
2007	3.9552
2008	3.7323
2009	5.8635
2010	5.9297
2011	6.2538
2012	5.9307
2013	5.4116
2014	4.4483
2015	3.8185
2016	4.1931
2017	4.012