Year Percent 1960-01-01 2.4333700000000000 1961-01-01 1.6991700000000000 1962-01-01 1.5786200000000001 1963-01-01 1.9764400000000002 1964-01-01 2.2085800000000000 1965-01-01 2.6625300000000000 1966-01-01 2.7495500000000000 1967-01-01 3.2915000000000000 1968-01-01 3.9589900000000000 1969-01-01 4.0249000000000000 1970-01-01 3.7340699999999996 1971-01-01 2.9288500000000000 1972-01-01 1.6511799999999999 1973-01-01 1.3040800000000000 1974-01-01 2.1521800000000000 1975-01-01 3.9167199999999998 1976-01-01 4.4871700000000000 1977-01-01 3.8258099999999997 1978-01-01 3.7652900000000002 1979-01-01 3.9067700000000000 1980-01-01 3.9759700000000000 1981-01-01 4.4699300000000010 1982-01-01 5.0406800000000000 1983-01-01 5.0522700000000000 1984-01-01 4.7289699999999995 1985-01-01 4.1413400000000005 1986-01-01 3.4875900000000000 1987-01-01 3.2751799999999998 1988-01-01 3.1452900000000000 1989-01-01 3.0485900000000004 1990-01-01 3.8394900000000000 1991-01-01 3.8453300000000000 1992-01-01 3.5060700000000000 1993-01-01 4.1108199999999995 1994-01-01 4.3353100000000000 1995-01-01 4.5918700000000000 1996-01-01 5.3616100000000000 1997-01-01 6.0396600000000000 1998-01-01 9.5382900000000000 1999-01-01 12.5824000000000000 2000-01-01 11.1187000000000000 2001-01-01 12.6882000000000000 2002-01-01 15.7641000000000000 2003-01-01 17.2929000000000000 2004-01-01 18.3068000000000000 2005-01-01 18.7744000000000000 2006-01-01 17.2473000000000000 2007-01-01 14.3638000000000000 2008-01-01 13.2115000000000000 2009-01-01 14.2100000000000000 2010-01-01 15.2799000000000000 2011-01-01 17.4914000000000000 2012-01-01 21.0633000000000000 2013-01-01 29.0915000000000000 2014-01-01 41.4922000000000000 2015-01-01 52.7697000000000000 2016-01-01 65.7878000000000000