Year Percent 1960-01-01 11.5451000000000000 1961-01-01 11.1117000000000000 1962-01-01 10.6222000000000000 1963-01-01 8.3336600000000000 1964-01-01 6.2669900000000000 1965-01-01 6.3537700000000000 1966-01-01 5.7391100000000000 1967-01-01 4.9747600000000000 1968-01-01 4.0587400000000000 1969-01-01 3.2794600000000000 1970-01-01 2.8644300000000000 1971-01-01 2.3759300000000000 1972-01-01 3.6095400000000000 1973-01-01 4.2304300000000000 1974-01-01 4.4095200000000000 1975-01-01 5.8611000000000000 1976-01-01 6.0519500000000000 1977-01-01 5.6341000000000000 1978-01-01 5.2134700000000000 1979-01-01 4.5260700000000000 1980-01-01 3.7878500000000000 1981-01-01 3.6316000000000000 1982-01-01 3.9549300000000005 1983-01-01 3.8599699999999997 1984-01-01 3.5808100000000000 1985-01-01 3.1702000000000000 1986-01-01 2.7395800000000000 1987-01-01 2.3582600000000000 1988-01-01 2.1989400000000003 1989-01-01 2.0662400000000000 1990-01-01 1.5818200000000000 1991-01-01 1.2511100000000000 1992-01-01 1.1070700000000000 1993-01-01 0.9969969999999999 1994-01-01 0.8916050000000000 1995-01-01 0.6744140000000001 1996-01-01 0.5375580000000000 1997-01-01 0.9747889999999999 1998-01-01 2.1748800000000000 1999-01-01 2.0272900000000003 2000-01-01 1.2697000000000000 2001-01-01 1.1225399999999999 2002-01-01 1.0171700000000001 2003-01-01 0.9261120000000000 2004-01-01 0.6931520000000000 2005-01-01 0.6423020000000000 2006-01-01 0.9004770000000001 2007-01-01 1.1111900000000000 2008-01-01 1.2334300000000000 2009-01-01 1.2668500000000000 2010-01-01 1.2446700000000002 2011-01-01 1.2289800000000000 2012-01-01 1.3660900000000000 2013-01-01 1.4893600000000000 2014-01-01 1.4806200000000000 2015-01-01 1.3695500000000000 2016-01-01 1.1334200000000000