Year Percent 1991-01-01 2.6660400000000000 1992-01-01 3.1150000000000000 1993-01-01 4.2052900000000000 1994-01-01 4.0941600000000000 1995-01-01 3.8770400000000000 1996-01-01 3.7947599999999997 1997-01-01 2.8605800000000000 1998-01-01 2.7707400000000000 1999-01-01 2.1304200000000000 2000-01-01 2.2313500000000000 2001-01-01 3.1022100000000000 2002-01-01 3.4291500000000000 2003-01-01 2.9977000000000000 2004-01-01 2.8426600000000000 2005-01-01 4.0963000000000000 2006-01-01 4.0218000000000000 2007-01-01 4.0810200000000000 2008-01-01 4.1101300000000010 2009-01-01 4.1616700000000000 2010-01-01 3.9918699999999996 2011-01-01 4.0751599999999994 2012-01-01 4.0247500000000000 2013-01-01 4.1263800000000000 2014-01-01 4.0121900000000000 2015-01-01 3.7892300000000003