Year Percent 1964-01-01 90.98840000000000 1965-01-01 83.43570000000000 1966-01-01 65.65610000000000 1967-01-01 56.02750000000000 1968-01-01 61.43680000000000 1969-01-01 89.19540000000000 1970-01-01 85.32190000000000 1971-01-01 108.39800000000000 1972-01-01 132.16000000000000 1973-01-01 148.67100000000000 1974-01-01 160.29399999999998 1975-01-01 166.42700000000002 1976-01-01 158.58000000000000 1977-01-01 147.50500000000000 1978-01-01 142.83200000000000 1979-01-01 148.46900000000000 1980-01-01 150.16500000000000 1981-01-01 153.57600000000000 1982-01-01 148.70900000000000 1983-01-01 140.33400000000000 1984-01-01 136.96800000000000 1985-01-01 133.41700000000000 1986-01-01 135.36900000000000 1987-01-01 131.37000000000000 1988-01-01 120.85500000000000 1989-01-01 120.05900000000000 1990-01-01 125.20400000000000 1991-01-01 131.71900000000000 1992-01-01 87.06320000000000 1993-01-01 22.72180000000000 1994-01-01 20.74660000000000 1995-01-01 21.44110000000000 1996-01-01 22.83170000000000 1997-01-01 20.23960000000000 1998-01-01 16.11600000000000 1999-01-01 17.39080000000000 2000-01-01 20.86020000000000 2001-01-01 20.90130000000000 2002-01-01 23.57050000000000 2003-01-01 25.71840000000000 2004-01-01 25.33820000000000 2005-01-01 28.72260000000000 2006-01-01 30.39010000000000 2007-01-01 28.68360000000000 2008-01-01 28.27350000000000 2009-01-01 30.89090000000000 2010-01-01 33.58230000000000 2011-01-01 32.73470000000000 2012-01-01 32.86090000000000 2013-01-01 36.01780000000000 2014-01-01 37.48880000000000 2015-01-01 40.16790000000000 2016-01-01 46.19270000000000