Year	Percent
1979	8.1903
1980	7.8632
1981	7.4302
1982	8.5254
1983	10.3694
1984	9.4769
1985	8.7628
1986	8.7067
1987	8.6247
1988	7.8992
1989	6.8413
1990	7.1922
1991	9.1495
1992	9.9276
1993	9.9974
1994	9.3612
1995	8.1053
1996	8.2359
1997	8.071
1998	7.3281
1999	6.6584
2000	6.0617
2001	6.4453
2002	6.1624
2003	5.9785
2004	5.5354
2005	5.22
2006	4.9217
2007	4.7841
2008	4.5704
2009	5.401
2010	5.3755
2011	5.3041
2012	5.326
2013	5.6104
2014	6.1721
2015	6.0722
2016	5.7795
2017	5.6682