Year	Percent
1960	10.05046
1961	10.05601
1962	10.09458
1963	10.17362
1964	10.30339
1965	10.48623
1966	10.68443
1967	10.86531
1968	11.04746
1969	11.2468
1970	11.49643
1971	11.56464
1972	11.45568
1973	11.35057
1974	11.26887
1975	11.25311
1976	11.29681
1977	11.31438
1978	11.29259
1979	11.24924
1980	11.18405
1981	11.35415
1982	11.71261
1983	12.10119
1984	12.51201
1985	12.92483
1986	13.3414
1987	13.75657
1988	14.17025
1989	14.58413
1990	14.97813
1991	15.11711
1992	15.10783
1993	15.1271
1994	15.16383
1995	15.22025
1996	15.31175
1997	15.43433
1998	15.54935
1999	15.6371
2000	15.7122
2001	15.77964
2002	15.83074
2003	15.88431
2004	15.94701
2005	16.01696
2006	16.08956
2007	16.11952
2008	16.08903
2009	16.06152
2010	16.06766
2011	16.0625
2012	16.06563
2013	16.05414
2014	16.03163
2015	16.02225
2016	16.02053
2017	16.01741