Year	Percent
1975	8.77218
1976	9.22909
1977	9.85776
1978	11.94576
1979	13.1492
1980	12.53779
1981	11.19768
1982	10.65481
1983	13.4401
1984	14.02112
1985	12.56425
1986	12.32785
1987	10.82933
1988	10.81068
1989	12.69922
1990	11.70866
1991	9.99113
1992	10.92655
1993	10.05374
1994	18.14966
1995	19.50337
1996	19.33273
1997	17.14368
1998	16.86446
1999	17.59258
2000	18.61957
2001	18.69982
2002	17.9893
2003	17.34294
2004	16.88511
2005	16.86687
2006	15.44363
2007	15.78119
2008	15.42978
2009	16.60639
2010	17.94584
2011	19.05806
2012	18.86085
2013	16.38085
2014	16.14667
2015	16.92471
2016	17.26813