Year	Percent
1983	7.7929
1984	8.2382
1985	9.6341
1986	9.3617
1987	9.3706
1988	7.8338
1989	6.6437
1990	6.0667
1991	6.4985
1992	6.7618
1993	6.6619
1994	6.4327
1995	6.0823
1996	5.6228
1997	4.9168
1998	4.5692
1999	4.3808
2000	4.0432
2001	3.5505
2002	3.7933
2003	3.291
2004	3.3873
2005	3.2689
2006	3.8863
2007	3.8256
2008	3.9531
2009	5.0936
2010	5.4573
2011	5.8929
2012	6.0129
2013	5.5344
2014	4.6421
2015	4.1279
2016	3.8556
2017	3.3918