Year	Percent
1960	9.53094
1961	9.63861
1962	9.75
1963	9.86685
1964	9.99268
1965	10.12743
1966	10.27363
1967	10.42966
1968	10.59428
1969	10.76294
1970	10.97436
1971	11.41005
1972	11.86578
1973	12.33983
1974	12.83768
1975	13.28905
1976	13.40048
1977	13.51469
1978	13.63265
1979	13.75241
1980	13.85842
1981	13.88641
1982	13.9157
1983	13.94614
1984	13.97881
1985	14.01262
1986	14.04935
1987	14.08904
1988	14.13379
1989	14.1837
1990	14.24963
1991	14.36344
1992	14.48625
1993	14.61557
1994	14.75253
1995	14.89593
1996	14.79176
1997	14.64272
1998	14.50093
1999	14.36527
2000	14.24456
2001	14.17221
2002	14.1046
2003	14.04459
2004	13.99647
2005	13.96148
2006	13.94134
2007	13.93355
2008	14.03277
2009	14.14304
2010	14.23502
2011	14.23617
2012	14.236
2013	14.23537
2014	14.23798
2015	14.2454
2016	14.25822
2017	14.27537