Year	Percent
1972	11.04115
1973	10.17335
1974	12.58381
1975	11.19387
1976	10.78384
1977	11.60892
1978	11.66141
1979	12.37413
1980	13.14315
1981	13.47698
1982	12.64056
1983	14.13958
1984	14.10679
1985	13.68784
1986	13.61615
1987	13.64999
1988	14.80673
1989	15.58057
1990	16.90732
1991	17.4135
1992	15.59178
1993	15.39922
1994	16.03569
1995	16.44095
1996	16.72621
1997	16.10552
1998	13.78815
1999	12.88923
2000	12.97673
2001	13.07019
2002	13.47031
2003	14.48157
2004	14.85335
2005	16.06186
2006	15.63697
2007	15.14315
2008	15.38488
2009	14.19425
2010	14.93264
2011	16.36185
2012	15.44094
2013	16.90911
2014	15.62227
2015	16.02809
2016	15.5099