Year Percent 1983-01-01 2.7252500000000000 1984-01-01 2.8068800000000000 1985-01-01 2.7117299999999998 1986-01-01 2.6268599999999998 1987-01-01 2.5145299999999997 1988-01-01 2.7304500000000000 1989-01-01 3.6275699999999995 1990-01-01 4.2115100000000000 1991-01-01 4.7966900000000000 1992-01-01 6.0985700000000000 1993-01-01 6.7708000000000000 1994-01-01 7.6864800000000000 1995-01-01 8.0554399999999990 1996-01-01 7.0917200000000000 1997-01-01 8.8716500000000000 1998-01-01 10.2426000000000000 1999-01-01 8.7219600000000010 2000-01-01 7.6167899999999990 2001-01-01 9.3034699999999990 2002-01-01 10.6371000000000000 2003-01-01 14.6584000000000000 2004-01-01 18.9124000000000000 2005-01-01 21.3949000000000000 2006-01-01 24.4200000000000000 2007-01-01 27.1859000000000000 2008-01-01 32.2248000000000000 2009-01-01 36.1928000000000000 2010-01-01 43.3946000000000000 2011-01-01 51.2171000000000000 2012-01-01 53.9885000000000000 2013-01-01 52.9456000000000000 2014-01-01 52.2754000000000000 2015-01-01 53.1889000000000000 2016-01-01 56.6024000000000000