Year	Percent
1983	18.8268
1984	20.0596
1985	23.3522
1986	22.6272
1987	22.8063
1988	22.8055
1989	19.5727
1990	18.2204
1991	21.0727
1992	20.7816
1993	22.7549
1994	20.5264
1995	17.3462
1996	16.9996
1997	14.8711
1998	10.9584
1999	8.428
2000	6.9023
2001	5.7638
2002	6.5979
2003	7.054
2004	7.5469
2005	7.9571
2006	8.1114
2007	7.8686
2008	10.0532
2009	16.7962
2010	20.8952
2011	22.3302
2012	23.5358
2013	22.7155
2014	19.7854
2015	16.3486
2016	13.5415
2017	12.6274