Year	Percent
1983	4.1983
1984	5.2277
1985	5.9781
1986	6.4268
1987	6.7299
1988	6.4369
1989	5.9572
1990	5.7478
1991	5.9439
1992	6.7893
1993	8.0839
1994	9.4806
1995	8.7002
1996	9.1884
1997	9.5596
1998	9.0811
1999	8.8177
2000	7.4412
2001	6.045
2002	6.7151
2003	6.6987
2004	6.9922
2005	6.6099
2006	6.4983
2007	6.1304
2008	5.4502
2009	6.9893
2010	7.2732
2011	7.3236
2012	8.1156
2013	8.7625
2014	9.18
2015	9.4847
2016	8.8572
2017	8.1535