Year	Percent
1960	2.82597
1961	2.8478
1962	2.8671
1963	2.88437
1964	2.89948
1965	2.91145
1966	2.92004
1967	2.92357
1968	2.91867
1969	2.90524
1970	2.88487
1971	2.86202
1972	2.8379
1973	2.80994
1974	2.77853
1975	2.74485
1976	2.71084
1977	2.67764
1978	2.64598
1979	2.61597
1980	2.58813
1981	2.55897
1982	2.53083
1983	2.50935
1984	2.49627
1985	2.48733
1986	2.47765
1987	2.46295
1988	2.44302
1989	2.41637
1990	2.38395
1991	2.34933
1992	2.31201
1993	2.2676
1994	2.21501
1995	2.15676
1996	2.10088
1997	2.04607
1998	1.98349
1999	1.91196
2000	1.83729
2001	1.75944
2002	1.69189
2003	1.65047
2004	1.64222
2005	1.65603
2006	1.67675
2007	1.68941
2008	1.68998
2009	1.67281
2010	1.64329
2011	1.61178
2012	1.58392
2013	1.55648
2014	1.53063
2015	1.50564
2016	1.47992
2017	1.45286