Year Percent 1960-01-01 1.7400799999999998 1961-01-01 1.6762599999999999 1962-01-01 2.3208800000000000 1963-01-01 2.7427799999999998 1964-01-01 2.3054500000000000 1965-01-01 2.0452200000000000 1966-01-01 1.8651000000000000 1967-01-01 1.6914900000000002 1968-01-01 2.4752300000000000 1969-01-01 3.4062099999999997 1970-01-01 4.2707300000000000 1971-01-01 3.2344700000000000 1972-01-01 2.5427400000000002 1973-01-01 2.7141100000000000 1974-01-01 2.5249000000000000 1975-01-01 2.3539200000000000 1976-01-01 2.4247900000000002 1977-01-01 2.1468700000000003 1978-01-01 4.4432700000000000 1979-01-01 8.0696700000000000 1980-01-01 10.5170000000000010 1981-01-01 13.8672000000000000 1982-01-01 17.5626000000000000 1983-01-01 32.2698000000000000 1984-01-01 41.2908000000000000 1985-01-01 29.4429000000000000 1986-01-01 16.7608000000000000 1987-01-01 10.4367000000000000 1988-01-01 9.6799400000000000 1989-01-01 0.8168440000000000 1990-01-01 5.5867100000000000 1991-01-01 4.0503800000000005 1992-01-01 56.1944000000000000 1993-01-01 90.9130000000000000 1994-01-01 87.5403000000000000 1995-01-01 74.7131000000000000 1996-01-01 56.9421000000000000 1997-01-01 48.5196000000000000 1998-01-01 49.3302000000000000 1999-01-01 44.5649000000000000 2000-01-01 43.5813000000000000 2001-01-01 50.7791000000000000 2002-01-01 59.6505000000000000 2003-01-01 57.3268000000000000 2004-01-01 51.2121000000000000 2005-01-01 45.5274000000000000 2006-01-01 40.6404000000000000 2007-01-01 34.9627000000000000 2008-01-01 31.3845000000000000 2009-01-01 30.9358000000000000 2010-01-01 28.7680000000000000 2011-01-01 24.7403000000000000 2012-01-01 22.4390000000000000 2013-01-01 21.1762000000000000 2014-01-01 18.5449000000000000 2015-01-01 16.0481000000000000 2016-01-01 14.8287000000000000