Year	Percent
1983	22.4217
1984	20.8211
1985	19.5976
1986	19.7542
1987	17.1976
1988	14.3457
1989	11.2268
1990	11.3994
1991	15.9376
1992	19.0297
1993	20.8527
1994	19.2991
1995	18.0125
1996	17.9215
1997	15.6455
1998	14.0015
1999	14.2488
2000	13.473
2001	11.7832
2002	12.8242
2003	13.0529
2004	11.6269
2005	14.3207
2006	15.6729
2007	15.8555
2008	17.0429
2009	21.8995
2010	21.9573
2011	23.7782
2012	23.9147
2013	23.0102
2014	18.9459
2015	16.1933
2016	14.7604
2017	13.4653