Year Percent 1980-01-01 0.6479070000000000 1981-01-01 0.7522730000000000 1982-01-01 1.1353100000000000 1983-01-01 1.2038600000000000 1984-01-01 1.4938500000000000 1985-01-01 2.0275300000000000 1986-01-01 2.6850099999999997 1987-01-01 3.0824000000000000 1988-01-01 2.9695900000000000 1989-01-01 2.7184900000000000 1990-01-01 2.6243900000000000 1991-01-01 2.6250700000000000 1992-01-01 2.4334599999999997 1993-01-01 2.3262099999999997 1994-01-01 2.5737200000000002 1995-01-01 3.2408000000000000 1996-01-01 4.1443600000000000 1997-01-01 4.9305500000000000 1998-01-01 6.4536200000000000 1999-01-01 8.2681399999999990 2000-01-01 10.3513000000000000 2001-01-01 14.6696000000000000 2002-01-01 16.8263000000000000 2003-01-01 18.3705000000000000 2004-01-01 18.9203000000000000 2005-01-01 17.9651000000000000 2006-01-01 20.7507000000000000 2007-01-01 23.9464000000000000 2008-01-01 23.6022000000000000 2009-01-01 23.5732000000000000 2010-01-01 21.6019000000000000 2011-01-01 19.3696000000000000 2012-01-01 18.3497000000000000 2013-01-01 17.8576000000000000 2014-01-01 17.5766000000000000 2015-01-01 17.6379000000000000 2016-01-01 17.7493000000000000