Year Percent 1960-01-01 50.43120000000000 1961-01-01 52.04160000000000 1962-01-01 54.99310000000000 1963-01-01 57.61950000000000 1964-01-01 62.62260000000000 1965-01-01 64.53570000000000 1966-01-01 64.27580000000000 1967-01-01 65.40950000000000 1968-01-01 67.62350000000000 1969-01-01 67.81160000000000 1970-01-01 65.90400000000000 1971-01-01 64.43710000000000 1972-01-01 64.24340000000000 1973-01-01 67.38360000000000 1974-01-01 71.25910000000000 1975-01-01 70.79650000000000 1976-01-01 71.62250000000000 1977-01-01 70.52400000000000 1978-01-01 66.75399999999999 1979-01-01 64.57970000000000 1980-01-01 63.79900000000000 1981-01-01 64.43480000000000 1982-01-01 64.24290000000000 1983-01-01 65.90640000000000 1984-01-01 67.07200000000000 1985-01-01 68.00320000000000 1986-01-01 69.67330000000000 1987-01-01 70.50950000000000 1988-01-01 71.82590000000000 1989-01-01 71.21380000000000 1990-01-01 69.02360000000000 1991-01-01 68.03560000000000 1992-01-01 70.57690000000000 1993-01-01 72.44170000000000 1994-01-01 73.61740000000000 1995-01-01 74.18140000000000 1996-01-01 73.39790000000000 1997-01-01 75.48410000000000 1998-01-01 75.81630000000000 1999-01-01 70.45880000000000 2000-01-01 67.35400000000000 2001-01-01 71.11660000000000 2002-01-01 80.78850000000000 2003-01-01 89.80770000000000 2004-01-01 88.65360000000000 2005-01-01 83.68030000000000 2006-01-01 83.18730000000000 2007-01-01 84.92770000000000 2008-01-01 79.92390000000000 2009-01-01 76.17510000000000 2010-01-01 77.97790000000000 2011-01-01 79.38180000000000 2012-01-01 81.53850000000000 2013-01-01 77.89540000000000 2014-01-01 76.21370000000000 2015-01-01 81.10000000000000 2016-01-01 82.37910000000000