Year Percent 1980-01-01 6.919220000000000 1981-01-01 7.706239999999999 1982-01-01 8.407190000000000 1983-01-01 9.085220000000000 1984-01-01 9.579150000000000 1985-01-01 11.071700000000000 1986-01-01 11.811700000000000 1987-01-01 15.306400000000000 1988-01-01 14.406400000000000 1989-01-01 14.819100000000000 1990-01-01 17.926300000000000 1991-01-01 23.854800000000000 1992-01-01 36.174600000000000 1993-01-01 47.084100000000000 1994-01-01 50.758999999999990 1995-01-01 38.915700000000000 1996-01-01 38.780800000000000 1997-01-01 35.549600000000000 1998-01-01 32.048600000000000 1999-01-01 30.046200000000000 2000-01-01 27.888500000000000 2001-01-01 28.724100000000000 2002-01-01 30.160400000000000 2003-01-01 36.748100000000000 2004-01-01 36.544800000000000 2005-01-01 32.794100000000000 2006-01-01 33.369000000000000 2007-01-01 26.727100000000000 2008-01-01 21.984700000000000 2009-01-01 32.304500000000000 2010-01-01 35.485400000000000 2011-01-01 36.385700000000000 2012-01-01 46.266100000000000 2013-01-01 51.744900000000000 2014-01-01 50.092000000000000 2015-01-01 60.080200000000000 2016-01-01 60.137100000000000