Year	Percent
1965	10.85327
1966	9.0317
1967	9.82073
1968	10.07946
1969	10.35692
1970	11.46214
1971	9.14075
1972	9.09442
1973	9.58973
1974	8.7055
1975	7.86314
1976	8.44544
1977	10.53819
1978	11.14433
1979	11.20414
1980	11.16869
1981	11.52818
1982	12.0466
1983	11.99348
1984	11.83295
1985	14.27253
1986	14.99892
1987	14.96148
1988	15.18217
1989	15.65493
1990	15.34675
1991	16.44736
1992	19.3983
1993	19.5205
1994	20.39173
1995	21.27387
1996	21.49305
1997	21.40043
1998	21.07597
1999	20.44112
2000	20.73557
2001	16.66089
2002	16.94682
2003	16.9713
2004	16.65732
2005	16.46709
2006	16.06797
2007	15.87314
2008	16.04999
2009	15.0668
2010	14.20076
2011	14.10764
2012	14.10206
2013	14.1546
2014	13.83145
2015	13.71712
2016	13.05536
2017	13.47802