Year	Percent
1980	13.17161
1981	12.63083
1982	14.10912
1983	14.2084
1984	15.31894
1985	14.06991
1986	12.94829
1987	10.59033
1988	9.38086
1989	8.30954
1990	8.26454
1991	9.36665
1992	11.44086
1993	11.95868
1994	13.61715
1995	11.94305
1996	11.94251
1997	11.94128
1998	11.94296
1999	11.94275
2000	11.23999
2001	11.94268
2002	11.81346
2003	11.81353
2004	11.81242
2005	11.81318
2006	11.65123
2007	10.88546
2008	12.49253
2009	11.78505
2010	11.80426
2011	11.40998
2012	11.31612
2013	11.06469
2014	10.94211
2015	10.76224