Year Percent 1960-01-01 53.89650000000000 1961-01-01 52.07300000000000 1962-01-01 48.91020000000000 1963-01-01 47.53040000000000 1964-01-01 47.20370000000000 1965-01-01 48.66640000000000 1966-01-01 48.84750000000000 1967-01-01 47.62330000000000 1968-01-01 46.85420000000000 1969-01-01 47.06399999999999 1970-01-01 49.31940000000000 1971-01-01 50.98320000000000 1972-01-01 53.16550000000000 1973-01-01 53.85090000000000 1974-01-01 56.22300000000000 1975-01-01 59.59830000000000 1976-01-01 57.41210000000000 1977-01-01 56.45080000000000 1978-01-01 59.56110000000000 1979-01-01 61.91890000000000 1980-01-01 50.09390000000000 1981-01-01 42.07600000000000 1982-01-01 44.65390000000000 1983-01-01 47.27870000000000 1984-01-01 53.79890000000000 1985-01-01 55.58900000000000 1986-01-01 52.78380000000000 1987-01-01 54.20350000000000 1988-01-01 55.05390000000000 1989-01-01 57.57680000000000 1990-01-01 64.22510000000000 1991-01-01 59.39070000000000 1992-01-01 52.59770000000000 1993-01-01 63.72650000000000 1994-01-01 72.73880000000000 1995-01-01 81.92420000000000 1996-01-01 86.45450000000000 1997-01-01 89.38230000000000 1998-01-01 91.92950000000000 1999-01-01 90.28250000000000 2000-01-01 85.14000000000000 2001-01-01 83.90810000000000 2002-01-01 86.48180000000000 2003-01-01 89.22250000000000 2004-01-01 88.78690000000000 2005-01-01 89.31720000000000 2006-01-01 91.61160000000000 2007-01-01 92.55440000000000 2008-01-01 90.75840000000000 2009-01-01 90.78610000000000 2010-01-01 94.58230000000000 2011-01-01 93.22600000000000 2012-01-01 92.36530000000000 2013-01-01 95.24140000000000 2014-01-01 95.66040000000000 2015-01-01 94.89560000000000 2016-01-01 95.19970000000000