Year Percent 1975-01-01 2.440220000000000000 1976-01-01 1.957540000000000000 1977-01-01 1.639970000000000100 1978-01-01 1.737709999999999900 1979-01-01 2.145880000000000000 1980-01-01 2.549990000000000000 1981-01-01 2.598580000000000000 1982-01-01 2.864330000000000000 1983-01-01 2.728940000000000000 1984-01-01 3.819509999999999700 1985-01-01 4.941560000000000000 1986-01-01 4.382810000000000000 1987-01-01 4.070280000000000000 1988-01-01 3.216740000000000000 1989-01-01 2.771920000000000000 1990-01-01 2.500909999999999700 1991-01-01 2.484870000000000000 1992-01-01 1.757170000000000100 1993-01-01 1.124420000000000000 1994-01-01 0.962526000000000000 1995-01-01 0.950167000000000000 1996-01-01 1.311180000000000000 1997-01-01 1.300290000000000000 1998-01-01 0.928436000000000000 1999-01-01 0.857382000000000000 2000-01-01 0.809721000000000000 2001-01-01 0.677729000000000000 2002-01-01 0.506003000000000000 2003-01-01 0.429951000000000000 2004-01-01 0.368807000000000000 2005-01-01 0.344079000000000000 2006-01-01 0.264482000000000000 2007-01-01 0.258957000000000000 2008-01-01 0.262633000000000000 2009-01-01 0.137702000000000000 2010-01-01 0.056104999999999995 2011-01-01 0.045879000000000000 2012-01-01 0.052745000000000010 2013-01-01 0.485069000000000000 2014-01-01 1.075189999999999900 2015-01-01 0.576805000000000000