Year Percent 1960-01-01 0.8193920000000000 1961-01-01 0.8791209999999999 1962-01-01 0.9580840000000000 1963-01-01 1.0620600000000000 1964-01-01 0.9572240000000000 1965-01-01 0.9016390000000000 1966-01-01 1.9543099999999998 1967-01-01 2.2194599999999998 1968-01-01 1.2065500000000000 1969-01-01 2.1723800000000000 1970-01-01 3.5181400000000003 1971-01-01 3.6444199999999998 1972-01-01 4.1900900000000005 1973-01-01 9.1786300000000000 1974-01-01 7.2963100000000010 1975-01-01 3.8068800000000005 1976-01-01 13.8641000000000000 1977-01-01 27.0284000000000000 1978-01-01 29.6145000000000000 1979-01-01 37.5372000000000000 1980-01-01 49.7600000000000000 1981-01-01 58.4023000000000000 1982-01-01 87.1076000000000000 1983-01-01 124.8300000000000000 1984-01-01 133.7900000000000000 1985-01-01 143.5580000000000000 1986-01-01 167.2400000000000000 1987-01-01 116.1439999999999900 1988-01-01 140.4489999999999800 1989-01-01 104.7239999999999900 1990-01-01 111.0550000000000000 1991-01-01 82.3827000000000000 1992-01-01 114.5370000000000000 1993-01-01 118.6150000000000000 1994-01-01 95.5092000000000000 1995-01-01 88.0018000000000000 1996-01-01 72.6808000000000000 1997-01-01 53.0811000000000000 1998-01-01 44.6727000000000000 1999-01-01 38.0015000000000000 2000-01-01 37.4564000000000000 2001-01-01 30.7972000000000000 2002-01-01 24.5093000000000000 2003-01-01 23.6739000000000000 2004-01-01 21.7968000000000000 2005-01-01 20.0932000000000000 2006-01-01 18.4865000000000000 2007-01-01 15.9192000000000000 2008-01-01 13.6354000000000000 2009-01-01 12.8054000000000000 2010-01-01 11.2076000000000000 2011-01-01 9.6994500000000000 2012-01-01 8.5490800000000000 2013-01-01 8.1394100000000000 2014-01-01 7.7258000000000000 2015-01-01 8.0464600000000000 2016-01-01 10.0149000000000000