Year Percent 1970-01-01 8.55123 1971-01-01 9.48355 1972-01-01 10.91860 1973-01-01 11.18900 1974-01-01 10.61500 1975-01-01 11.67880 1976-01-01 13.91690 1977-01-01 13.56390 1978-01-01 12.98000 1979-01-01 13.76780 1980-01-01 12.93110 1981-01-01 12.43190 1982-01-01 11.21750 1983-01-01 12.12990 1984-01-01 13.00410 1985-01-01 13.69130 1986-01-01 14.33580 1987-01-01 14.70010 1988-01-01 16.88930 1989-01-01 18.02640 1990-01-01 18.42630 1991-01-01 18.00710 1992-01-01 18.82750 1993-01-01 18.83340 1994-01-01 17.89460 1995-01-01 15.58160 1996-01-01 14.88420 1997-01-01 15.36350 1998-01-01 16.33170 1999-01-01 17.28870 2000-01-01 16.54590 2001-01-01 14.53600 2002-01-01 14.63140 2003-01-01 14.88240 2004-01-01 15.33320 2005-01-01 14.98590 2006-01-01 16.04130 2007-01-01 18.34500 2008-01-01 19.82930 2009-01-01 21.50570 2010-01-01 23.43060 2011-01-01 22.77480 2012-01-01 21.96460 2013-01-01 22.64500 2014-01-01 23.20440 2015-01-01 23.79820 2016-01-01 25.79030