Year Percent 1990-01-01 3.2626000000000000 1991-01-01 2.9165500000000000 1992-01-01 2.7988900000000000 1993-01-01 2.8167800000000000 1994-01-01 2.5791000000000000 1995-01-01 2.5147200000000000 1996-01-01 2.8892900000000004 1997-01-01 3.5112000000000000 1998-01-01 5.0118500000000000 1999-01-01 6.4423300000000000 2000-01-01 7.4836199999999990 2001-01-01 7.8821900000000000 2002-01-01 9.8029000000000000 2003-01-01 11.3775000000000000 2004-01-01 16.7469000000000000 2005-01-01 24.2921000000000000 2006-01-01 28.7874000000000000 2007-01-01 28.4818000000000000 2008-01-01 32.9550000000000000 2009-01-01 33.2886000000000000 2010-01-01 32.8672000000000000 2011-01-01 30.4528000000000000 2012-01-01 34.1863000000000000 2013-01-01 34.7156000000000000 2014-01-01 37.4525000000000000 2015-01-01 45.4843000000000000 2016-01-01 52.4698000000000000