Year Percent 1980-01-01 0.28742700000000000 1981-01-01 0.26765000000000000 1982-01-01 0.37404299999999996 1983-01-01 0.52775000000000000 1984-01-01 0.41456700000000000 1985-01-01 1.41610000000000000 1986-01-01 1.38306000000000000 1987-01-01 1.28231000000000000 1988-01-01 1.07815000000000000 1989-01-01 0.87656499999999990 1990-01-01 0.89577700000000000 1991-01-01 0.63947900000000000 1992-01-01 0.59152700000000000 1993-01-01 2.90837999999999970 1994-01-01 4.06424000000000000 1995-01-01 4.24813000000000100 1996-01-01 6.37226000000000000 1997-01-01 8.36793999999999900 1998-01-01 11.42760000000000000 1999-01-01 9.40255000000000000 2000-01-01 8.63315000000000000 2001-01-01 6.78961999999999900 2002-01-01 5.55468000000000000 2003-01-01 4.24220000000000000 2004-01-01 3.38334000000000000 2005-01-01 3.84071000000000000 2006-01-01 3.71346999999999960 2007-01-01 3.03213000000000000 2008-01-01 2.86068000000000000 2009-01-01 2.54208000000000000 2010-01-01 2.49524000000000030 2011-01-01 2.62768000000000000 2012-01-01 4.00233000000000100 2013-01-01 4.32479000000000000 2014-01-01 5.15793000000000000 2015-01-01 4.84794000000000000 2016-01-01 4.86963000000000000