Year	Percent
1960	1.273
1961	1.4187
1962	1.57383
1963	1.71662
1964	1.83282
1965	1.9265
1966	2.02402
1967	2.11938
1968	2.1826
1969	2.20561
1970	2.20265
1971	2.19481
1972	2.19606
1973	2.20365
1974	2.22123
1975	2.24912
1976	2.26207
1977	2.27782
1978	2.33772
1979	2.45199
1980	2.59221
1981	2.73934
1982	2.84585
1983	2.87521
1984	2.81068
1985	2.68442
1986	2.53364
1987	2.40109
1988	2.30296
1989	2.25444
1990	2.2338
1991	2.22089
1992	2.18024
1993	2.08958
1994	1.93573
1995	1.74187
1996	1.5467
1997	1.37463
1998	1.22058
1999	1.09247
2000	0.98903
2001	0.88791
2002	0.80026
2003	0.76098
2004	0.7809
2005	0.84375
2006	0.92277
2007	0.99493
2008	1.05528
2009	1.09416
2010	1.11615
2011	1.13579
2012	1.1567
2013	1.16789
2014	1.16751
2015	1.15761
2016	1.14291
2017	1.12386