Year Percent 1961-01-01 12.875100000000000 1962-01-01 12.213500000000000 1963-01-01 12.260700000000000 1964-01-01 11.388600000000000 1965-01-01 10.551100000000000 1966-01-01 10.444700000000000 1967-01-01 10.109600000000000 1968-01-01 9.696710000000001 1969-01-01 9.015780000000000 1970-01-01 9.527239999999999 1971-01-01 10.405999999999999 1972-01-01 11.846700000000000 1973-01-01 14.057500000000000 1974-01-01 13.123700000000000 1975-01-01 11.920500000000000 1976-01-01 14.409500000000000 1977-01-01 16.292400000000000 1978-01-01 17.950900000000000 1979-01-01 17.797500000000000 1980-01-01 14.934600000000000 1981-01-01 11.768100000000000 1982-01-01 11.887900000000000 1983-01-01 14.413400000000000 1984-01-01 14.218300000000000 1985-01-01 14.194200000000000 1986-01-01 15.563800000000000 1987-01-01 14.827800000000000 1988-01-01 15.005999999999998 1989-01-01 23.473700000000000 1990-01-01 23.473700000000000 1991-01-01 47.348900000000000 1992-01-01 96.753200000000000 1993-01-01 216.280000000000000 1994-01-01 342.589000000000000 1995-01-01 373.721000000000000 1996-01-01 266.854000000000040 1997-01-01 112.943000000000000 1998-01-01 234.537999999999980 1999-01-01 329.772000000000000 2000-01-01 219.382000000000000 2001-01-01 213.845000000000000 2002-01-01 244.619000000000030 2003-01-01 371.573000000000040 2004-01-01 403.135000000000000 2005-01-01 529.604000000000000 2006-01-01 661.663000000000000 2007-01-01 763.781000000000100 2008-01-01 21.466100000000000 2009-01-01 21.795200000000000 2010-01-01 25.727200000000000 2011-01-01 28.786300000000000 2012-01-01 28.874900000000000 2013-01-01 28.491000000000000