Year	Percent
1983	10.4611
1984	12.0936
1985	12.6295
1986	12.2687
1987	13.4674
1988	12.7903
1989	12.5931
1990	12.1615
1991	11.6116
1992	12.83
1993	13.4029
1994	14.4851
1995	14.0543
1996	14.4857
1997	14.4202
1998	14.1068
1999	13.9005
2000	12.1941
2001	10.5107
2002	9.7993
2003	9.1315
2004	9.8754
2005	9.2695
2006	9.1109
2007	8.0862
2008	7.4422
2009	8.8021
2010	9.066
2011	9.116
2012	9.3585
2013	9.7892
2014	10.0297
2015	9.884
2016	9.8534
2017	9.336