Year Percent 1988-01-01 1.2812600000000000 1989-01-01 1.5805300000000000 1990-01-01 1.4946300000000000 1991-01-01 1.6807700000000000 1992-01-01 2.4677300000000000 1993-01-01 3.3328900000000004 1994-01-01 4.8927900000000000 1995-01-01 4.2438600000000000 1996-01-01 3.8433800000000002 1997-01-01 3.8542400000000003 1998-01-01 4.2143100000000000 1999-01-01 5.5474000000000000 2000-01-01 7.1771300000000000 2001-01-01 8.6411100000000010 2002-01-01 8.8813200000000000 2003-01-01 8.1676600000000000 2004-01-01 7.1706199999999995 2005-01-01 6.8672900000000000 2006-01-01 7.6592400000000000 2007-01-01 7.2020800000000005 2008-01-01 6.2731100000000000 2009-01-01 7.6872800000000000 2010-01-01 7.2690300000000000 2011-01-01 6.9587900000000000 2012-01-01 8.2468000000000000 2013-01-01 9.2677100000000010 2014-01-01 11.1457000000000000 2015-01-01 11.8662000000000000 2016-01-01 12.6685000000000000