Year	Percent
1972	11.78916
1973	11.46968
1974	11.81024
1975	11.15918
1976	10.72494
1977	11.59567
1978	11.51801
1979	11.98187
1980	12.11631
1981	12.53521
1982	11.97432
1983	10.33661
1984	10.15197
1985	10.36571
1986	10.13974
1987	10.91512
1988	10.56328
1989	10.75173
1990	10.4365
1991	10.29374
1992	9.9552
1993	10.27473
1994	10.59223
1995	10.94616
1996	11.33589
1997	11.78566
1998	12.29408
1999	12.22261
2000	12.92813
2001	11.81317
2002	9.82432
2003	9.34276
2004	9.49263
2005	10.6371
2006	11.27456
2007	11.2885
2008	10.30845
2009	7.93591
2010	8.61081
2011	9.58908
2012	9.8211
2013	10.57721
2014	11.00162
2015	11.23938
2016	10.89325