Year Percent 1980-01-01 0.32415700000000003 1981-01-01 0.39506500000000000 1982-01-01 0.53118400000000000 1983-01-01 0.87240900000000000 1984-01-01 1.20385000000000000 1985-01-01 1.76606000000000000 1986-01-01 2.50227000000000000 1987-01-01 3.06612000000000000 1988-01-01 3.40704000000000030 1989-01-01 4.03435000000000000 1990-01-01 3.82779000000000020 1991-01-01 3.85233000000000030 1992-01-01 3.97456000000000000 1993-01-01 5.21583000000000000 1994-01-01 7.00168999999999900 1995-01-01 8.37501000000000100 1996-01-01 11.31299999999999900 1997-01-01 14.92820000000000000 1998-01-01 18.70250000000000000 1999-01-01 23.68470000000000000 2000-01-01 34.55470000000000000 2001-01-01 38.89380000000000000 2002-01-01 47.82590000000000000 2003-01-01 51.68120000000000000 2004-01-01 55.66560000000000000 2005-01-01 54.07520000000000000 2006-01-01 64.10140000000000000 2007-01-01 64.73170000000000000 2008-01-01 57.42340000000000000 2009-01-01 63.03750000000000000 2010-01-01 58.64670000000000000 2011-01-01 53.66590000000000000 2012-01-01 57.79860000000000000 2013-01-01 54.04170000000000000 2014-01-01 48.76760000000000000 2015-01-01 50.73620000000000000 2016-01-01 48.49899999999999500