Year	Percent
1972	10.49697
1973	11.69104
1974	11.28771
1975	9.35349
1976	9.13088
1977	9.16233
1978	9.25383
1979	9.94527
1980	10.53001
1981	10.97977
1982	10.96142
1983	10.85695
1984	11.1303
1985	11.44489
1986	11.31143
1987	12.14667
1988	12.45397
1989	12.41775
1990	12.94729
1991	13.13319
1992	11.62717
1993	11.59076
1994	11.07305
1995	10.95823
1996	10.81458
1997	10.65163
1998	10.06754
1999	9.77331
2000	10.37226
2001	9.89593
2002	9.0616
2003	8.91896
2004	9.35269
2005	10.13701
2006	10.51274
2007	10.10619
2008	8.93159
2009	8.36891
2010	8.80978
2011	9.35682
2012	9.68241
2013	10.36062
2014	11.46921
2015	11.40927
2016	11.10336