Year Percent 1960-01-01 8.24244 1961-01-01 8.95618 1962-01-01 8.85135 1963-01-01 9.37464 1964-01-01 10.85760 1965-01-01 12.05520 1966-01-01 12.90240 1967-01-01 14.72720 1968-01-01 15.62430 1969-01-01 15.53940 1970-01-01 17.06480 1971-01-01 17.61960 1972-01-01 18.09040 1973-01-01 19.11180 1974-01-01 18.66170 1975-01-01 18.86890 1976-01-01 20.67640 1977-01-01 22.05590 1978-01-01 23.05480 1979-01-01 22.37940 1980-01-01 22.42680 1981-01-01 22.40660 1982-01-01 22.91710 1983-01-01 23.71460 1984-01-01 21.14760 1985-01-01 19.05960 1986-01-01 19.08360 1987-01-01 17.52600 1988-01-01 17.11550 1989-01-01 18.10950 1990-01-01 20.20280 1991-01-01 19.82830 1992-01-01 24.37900 1993-01-01 27.16780 1994-01-01 29.19150 1995-01-01 27.28350 1996-01-01 25.40470 1997-01-01 25.27580 1998-01-01 23.99580 1999-01-01 24.14080 2000-01-01 24.25910 2001-01-01 23.10940 2002-01-01 21.02230 2003-01-01 19.98890 2004-01-01 20.27880 2005-01-01 20.39960 2006-01-01 19.76840 2007-01-01 20.17120 2008-01-01 21.47600 2009-01-01 31.69960 2010-01-01 37.20920 2011-01-01 40.27750 2012-01-01 43.98930 2013-01-01 44.06790 2014-01-01 47.59430 2015-01-01 52.42080 2016-01-01 52.97850