Year Percent 1960-01-01 20.61460000000000 1961-01-01 20.85850000000000 1962-01-01 22.39760000000000 1963-01-01 23.55220000000000 1964-01-01 24.45580000000000 1965-01-01 26.30840000000000 1966-01-01 28.39260000000000 1967-01-01 28.42730000000000 1968-01-01 29.55780000000000 1969-01-01 33.83910000000000 1970-01-01 36.88070000000000 1971-01-01 40.91940000000000 1972-01-01 43.52940000000000 1973-01-01 43.29300000000000 1974-01-01 47.01790000000000 1975-01-01 50.36960000000000 1976-01-01 56.69200000000000 1977-01-01 62.63270000000000 1978-01-01 58.27690000000000 1979-01-01 63.38390000000000 1980-01-01 71.38900000000000 1981-01-01 78.89920000000000 1982-01-01 82.27120000000000 1983-01-01 81.01960000000000 1984-01-01 83.15790000000000 1985-01-01 84.11210000000000 1986-01-01 79.93920000000000 1987-01-01 78.49700000000000 1988-01-01 75.33700000000000 1989-01-01 73.98510000000000 1990-01-01 70.30070000000000 1991-01-01 71.13630000000000 1992-01-01 76.14960000000000 1993-01-01 81.78150000000000 1994-01-01 82.91040000000000 1995-01-01 83.77360000000000 1996-01-01 84.28850000000000 1997-01-01 82.16010000000000 1998-01-01 81.03130000000000 1999-01-01 85.93360000000000 2000-01-01 91.06090000000000 2001-01-01 90.45110000000000 2002-01-01 88.92630000000000 2003-01-01 89.02030000000000 2004-01-01 89.79799999999999 2005-01-01 91.67760000000000 2006-01-01 92.65570000000000 2007-01-01 92.45780000000000 2008-01-01 98.82590000000000 2009-01-01 101.45100000000001 2010-01-01 97.45130000000000 2011-01-01 100.27400000000000 2012-01-01 100.33900000000000 2013-01-01 95.45210000000000 2014-01-01 95.57940000000000 2015-01-01 95.18230000000000 2016-01-01 97.86830000000000