Year	Percent
1960-01-01	92.990
1961-01-01	92.670
1962-01-01	92.530
1963-01-01	93.560
1964-01-01	94.610
1965-01-01	95.210
1966-01-01	93.100
1967-01-01	94.060
1968-01-01	94.680
1969-01-01	95.590
1970-01-01	94.700
1971-01-01	94.570
1972-01-01	95.860
1973-01-01	97.340
1974-01-01	97.730
1975-01-01	95.830
1976-01-01	94.830
1977-01-01	94.950
1978-01-01	96.900
1979-01-01	95.090
1980-01-01	94.190
1981-01-01	94.720
1982-01-01	95.010
1983-01-01	95.310
1984-01-01	95.570
1985-01-01	96.170
1986-01-01	96.720
1987-01-01	97.025
1988-01-01	97.290
1989-01-01	97.550
1990-01-01	97.490
1991-01-01	96.410
1992-01-01	97.900
1993-01-01	98.130
1994-01-01	98.500
1995-01-01	98.590
1996-01-01	98.770
1997-01-01	98.920
1998-01-01	98.675
1999-01-01	99.560
2000-01-01	99.680
2001-01-01	99.685
2002-01-01	99.760
2003-01-01	99.700
2004-01-01	99.640
2005-01-01	99.545
2006-01-01	99.685
2007-01-01	99.720
2008-01-01	99.730
2009-01-01	99.650
2010-01-01	99.470
2011-01-01	99.370
2012-01-01	99.280
2013-01-01	99.145
2014-01-01	98.980
2015-01-01	96.940