Year	Percent
1983	19.3365
1984	20.4979
1985	17.6734
1986	15.5277
1987	14.6712
1988	12.9669
1989	11.3695
1990	10.1075
1991	11.0236
1992	11.309
1993	17.4076
1994	20.5458
1995	19.6657
1996	17.2766
1997	17.6191
1998	18.2696
1999	22.6864
2000	12.8711
2001	14.3212
2002	16.0312
2003	20.0714
2004	15.7564
2005	20.9997
2006	18.803
2007	17.1033
2008	17.3465
2009	21.4872
2010	22.4259
2011	18.7253
2012	20.435
2013	24.7058
2014	23.9883
2015	23.8014
2016	21.7479
2017	20.2274