Year Percent 1995-01-01 1.1390500000000000 1996-01-01 1.3518100000000000 1997-01-01 3.3192100000000000 1998-01-01 3.8888599999999998 1999-01-01 1.2717100000000001 2000-01-01 1.1400000000000000 2001-01-01 2.0069300000000000 2002-01-01 2.5157300000000000 2003-01-01 3.5918400000000004 2004-01-01 4.2356800000000000 2005-01-01 4.4918700000000000 2006-01-01 5.9120099999999995 2007-01-01 7.9478300000000010 2008-01-01 9.9139900000000000 2009-01-01 16.9704000000000000 2010-01-01 18.6506000000000000 2011-01-01 18.5313000000000000 2012-01-01 20.9566000000000000 2013-01-01 22.5006000000000000 2014-01-01 22.8972000000000000 2015-01-01 25.0094000000000000 2016-01-01 22.4375000000000000