Year	Percent
1976	10.94171
1977	13.53338
1978	11.24979
1979	8.08701
1980	7.96445
1981	10.12863
1982	15.50332
1983	22.33735
1984	25.73441
1985	28.19679
1986	27.87675
1987	28.27278
1988	21.80169
1989	18.67427
1990	21.66361
1991	27.46062
1992	24.14026
1993	21.7429
1994	20.87109
1995	17.87771
1996	18.84889
1997	12.76169
1998	19.72444
1999	14.66715
2000	14.24734
2001	14.84275
2002	17.72074
2003	24.23473
2004	30.26223
2005	25.13437
2006	31.55885
2007	23.99682
2008	20.2202
2009	27.44054
2010	21.52899
2011	21.61759
2012	18.61266
2013	17.10193
2014	18.83468
2015	17.75065
2016	19.88126