Year Percent 1961 1.68348 1962 0.87239 1963 3.84675 1964 5.25829 1965 -4.63466 1966 -2.1125 1967 5.5967 1968 1.22688 1969 4.26968 1970 2.86377 1971 -0.6272 1972 -2.81659 1973 0.91849 1974 -1.14679 1975 6.64622 1976 -0.65072 1977 4.82877 1978 3.3271 1979 -7.38325 1980 4.30515 1981 3.57805 1982 1.10103 1983 4.83544 1984 1.4711 1985 2.90843 1986 2.48029 1987 1.7237 1988 7.30296 1989 3.73699 1990 3.3669 1991 -0.98255 1992 3.3907 1993 2.70614 1994 4.60472 1995 5.52729 1996 5.5268 1997 2.11863 1998 4.24371 1999 6.89248 2000 2.01556 2001 3.02124 2002 2.05812 2003 6.08669 2004 6.18757 2005 7.56712 2006 7.58463 2007 8.15357 2008 2.37525 2009 6.95004 2010 8.76318 2011 5.24854 2012 4.13472 2013 5.09669 2014 6.14033 2015 6.89904 2016 5.88984 2017 5.42924