Year Percent 1960-01-01 4.46820000000000000 1961-01-01 4.09927000000000000 1962-01-01 3.97949000000000000 1963-01-01 4.30645999999999950 1964-01-01 4.37047000000000000 1965-01-01 4.83890000000000000 1966-01-01 5.34130000000000000 1967-01-01 5.99044000000000000 1968-01-01 6.58566000000000100 1969-01-01 6.64423999999999900 1970-01-01 6.49541000000000000 1971-01-01 7.34134000000000000 1972-01-01 8.59176000000000000 1973-01-01 8.96964000000000000 1974-01-01 9.08990000000000000 1975-01-01 9.46723999999999900 1976-01-01 8.60761000000000100 1977-01-01 8.24556999999999900 1978-01-01 8.07333000000000000 1979-01-01 5.48311000000000000 1980-01-01 5.28094000000000000 1981-01-01 5.87116999999999900 1982-01-01 6.97390000000000000 1983-01-01 7.90270000000000000 1984-01-01 7.53523999999999900 1985-01-01 6.91011000000000000 1986-01-01 5.89234000000000000 1987-01-01 5.54871000000000000 1988-01-01 4.57978000000000000 1989-01-01 2.47546000000000000 1990-01-01 1.78983000000000000 1991-01-01 1.67730999999999990 1992-01-01 1.72605000000000000 1993-01-01 1.26230000000000000 1994-01-01 0.83849400000000010 1995-01-01 0.67604000000000000 1996-01-01 0.63711300000000000 1997-01-01 0.58636800000000000 1998-01-01 0.57445400000000000 1999-01-01 0.51666499999999990 2000-01-01 0.44290700000000000 2001-01-01 0.39015300000000000 2002-01-01 0.33963200000000000 2003-01-01 0.32958000000000004 2004-01-01 0.31083200000000000 2005-01-01 0.29570799999999997 2006-01-01 0.26480500000000000 2007-01-01 0.23861999999999997 2008-01-01 0.22626300000000002 2009-01-01 0.22715600000000000 2010-01-01 0.19779300000000000 2011-01-01 0.17722600000000000