Year Percent 1978-01-01 24.302500000000000 1979-01-01 32.081600000000000 1980-01-01 44.258200000000000 1981-01-01 64.523200000000000 1982-01-01 75.572500000000000 1983-01-01 60.993300000000000 1984-01-01 56.059400000000000 1985-01-01 74.108700000000000 1986-01-01 89.466000000000010 1987-01-01 77.213400000000000 1988-01-01 66.431000000000000 1989-01-01 75.834300000000000 1990-01-01 80.587400000000000 1991-01-01 62.248200000000000 1992-01-01 46.588100000000000 1993-01-01 41.740400000000000 1994-01-01 42.660000000000000 1995-01-01 43.663999999999994 1996-01-01 42.652900000000000 1997-01-01 41.702600000000000 1998-01-01 47.350700000000000 1999-01-01 53.707000000000000 2000-01-01 54.412200000000000 2001-01-01 52.386000000000000 2002-01-01 52.013900000000000 2003-01-01 53.123200000000000 2004-01-01 50.850200000000000 2005-01-01 52.796800000000000 2006-01-01 63.022400000000000 2007-01-01 78.862200000000000 2008-01-01 95.732100000000000 2009-01-01 91.372999999999990 2010-01-01 75.000900000000000 2011-01-01 63.629900000000000 2012-01-01 53.834900000000000 2013-01-01 50.200900000000000 2014-01-01 52.924400000000000 2015-01-01 56.002300000000000 2016-01-01 55.999800000000000