Year	Percent
1983	12.8817
1984	14.3466
1985	16.206
1986	15.5756
1987	15.8364
1988	15.6107
1989	15.1182
1990	12.7456
1991	14.2352
1992	14.0674
1993	14.1924
1994	13.2507
1995	11.044
1996	11.0398
1997	9.5282
1998	7.6171
1999	5.7063
2000	4.2944
2001	3.4293
2002	4.0617
2003	4.3945
2004	4.5907
2005	3.9988
2006	4.0793
2007	4.1617
2008	6.2658
2009	13.1492
2010	15.3895
2011	16.129
2012	15.8585
2013	13.3436
2014	11.3332
2015	9.4785
2016	7.9128
2017	6.223