Year Percent 1987-01-01 12.908900000000000 1988-01-01 11.810500000000000 1989-01-01 14.252800000000000 1990-01-01 10.631900000000000 1991-01-01 11.902000000000001 1992-01-01 13.727500000000000 1993-01-01 18.368500000000000 1994-01-01 17.500800000000000 1995-01-01 19.731200000000000 1996-01-01 21.995000000000000 1997-01-01 23.048800000000000 1998-01-01 23.879300000000000 1999-01-01 28.933900000000000 2000-01-01 22.080000000000000 2001-01-01 19.630000000000000 2002-01-01 16.440000000000000 2003-01-01 19.550000000000000 2004-01-01 20.620000000000000 2005-01-01 21.810000000000000 2006-01-01 28.200000000000000 2007-01-01 29.300000000000000 2008-01-01 17.550000000000000 2009-01-01 30.800000000000000 2010-01-01 35.170000000000000 2011-01-01 36.200000000000000 2012-01-01 43.710000000000000 2013-01-01 50.050000000000000 2014-01-01 50.060000000000000 2015-01-01 55.350000000000000 2016-01-01 57.700000000000000