Year Percent 1999-01-01 37.7460000000000000 2000-01-01 38.7260000000000000 2001-01-01 35.3655000000000000 2002-01-01 28.2036000000000000 2003-01-01 21.5821000000000000 2004-01-01 15.0363000000000000 2005-01-01 7.4469400000000000 2006-01-01 8.6311100000000010 2007-01-01 5.5858000000000000 2008-01-01 3.3705300000000005 2009-01-01 3.5456199999999995 2010-01-01 3.5675000000000000 2011-01-01 2.3625100000000000 2012-01-01 4.0776500000000000 2013-01-01 5.3063199999999995 2014-01-01 8.0694400000000000 2015-01-01 9.2186100000000000 2016-01-01 11.8993000000000000