Year	Percent
1960	2.68105
1961	2.42677
1962	2.32265
1963	2.27983
1964	2.23212
1965	2.17937
1966	2.12683
1967	2.08164
1968	2.07258
1969	2.10189
1970	2.16106
1971	2.18513
1972	2.22552
1973	2.241
1974	2.20437
1975	2.13171
1976	2.05041
1977	1.98165
1978	1.94279
1979	1.93822
1980	1.95912
1981	2.05718
1982	2.1003
1983	2.09463
1984	2.07614
1985	2.04319
1986	2.00727
1987	1.97391
1988	1.93947
1989	1.90101
1990	1.86199
1991	1.80295
1992	1.6247
1993	1.58473
1994	1.53924
1995	1.4874
1996	1.43563
1997	1.38668
1998	1.35104
1999	1.33254
2000	1.32425
2001	1.3207
2002	1.31139
2003	1.29885
2004	1.28243
2005	1.26055
2006	1.23807
2007	1.2183
2008	1.20722
2009	1.20506
2010	1.2091
2011	1.19994
2012	1.19425
2013	1.18765
2014	1.17289
2015	1.14765
2016	1.12016
2017	1.09452