Year Percent 1963-01-01 53.56980000000000 1964-01-01 52.44320000000000 1965-01-01 53.15920000000000 1966-01-01 54.79740000000000 1967-01-01 57.91150000000000 1968-01-01 61.00290000000000 1969-01-01 63.21120000000000 1970-01-01 61.94170000000000 1971-01-01 64.78670000000000 1972-01-01 68.89590000000000 1973-01-01 68.51500000000000 1974-01-01 64.35670000000000 1975-01-01 64.88480000000000 1976-01-01 61.11510000000000 1977-01-01 59.15390000000000 1978-01-01 56.74540000000000 1979-01-01 52.41690000000000 1980-01-01 49.68570000000000 1981-01-01 48.06940000000000 1982-01-01 46.32950000000000 1983-01-01 44.87380000000000 1984-01-01 45.04320000000000 1985-01-01 45.81470000000000 1986-01-01 45.62230000000000 1987-01-01 46.17100000000001 1988-01-01 47.01350000000000 1989-01-01 48.60590000000000 1990-01-01 49.45270000000000 1991-01-01 51.98900000000000 1992-01-01 55.47150000000000 1993-01-01 57.47870000000000 1994-01-01 55.42570000000000 1995-01-01 53.12510000000000 1996-01-01 51.97520000000000 1997-01-01 51.70800000000000 1998-01-01 53.35160000000000 1999-01-01 62.68600000000001 2000-01-01 70.33020000000000 2001-01-01 59.91570000000000 2002-01-01 60.33270000000000 2003-01-01 62.86600000000001 2004-01-01 65.30020000000000 2005-01-01 68.36680000000000 2006-01-01 72.11150000000000 2007-01-01 77.23090000000000 2008-01-01 82.95920000000000 2009-01-01 87.33870000000000 2010-01-01 89.65930000000000 2011-01-01 93.26150000000000 2012-01-01 95.66010000000000 2013-01-01 93.24390000000000 2014-01-01 89.68180000000000 2015-01-01 87.41530000000000 2016-01-01 85.41710000000000