Year	Percent
1972	10.82506
1973	10.96087
1974	10.51501
1975	10.08303
1976	10.20896
1977	10.53071
1978	10.53311
1979	10.4193
1980	10.32162
1981	10.09493
1982	9.83163
1983	9.78743
1984	10.22956
1985	10.23571
1986	9.97563
1987	10.12294
1988	9.85376
1989	10.28965
1990	9.86963
1991	11.67388
1992	11.8006
1993	11.47579
1994	11.67312
1995	11.45196
1996	10.87301
1997	10.6991
1998	10.81576
1999	11.47941
2000	11.66385
2001	10.92511
2002	10.78197
2003	10.95641
2004	10.3891
2005	10.59882
2006	10.81462
2007	11.27235
2008	11.39089
2009	11.55803
2010	11.11579
2011	11.44178
2012	11.57121
2013	11.55001
2014	11.48063
2015	11.36816
2016	11.24206