Year Percent 1960 -0.50801 1961 0.06739 1962 0.71968 1963 1.215 1964 1.6347 1965 1.93125 1966 2.08564 1967 1.7912 1968 1.87344 1969 1.79958 1970 1.62245 1971 1.16626 1972 -0.01278 1973 -0.15026 1974 -0.17612 1975 -0.10582 1976 0.42581 1977 1.65707 1978 1.54965 1979 1.18108 1980 0.62182 1981 -0.02431 1982 -0.55777 1983 -0.73932 1984 -0.3949 1985 0.32714 1986 1.17319 1987 1.84953 1988 2.16175 1989 2.00137 1990 1.52531 1991 0.96961 1992 0.56338 1993 0.28051 1994 0.24929 1995 0.37829 1996 0.53325 1997 0.63399 1998 0.74903 1999 0.79712 2000 0.84934 2001 0.89492 2002 0.95489 2003 1.00274 2004 1.03884 2005 1.06107 2006 1.07246 2007 1.08586 2008 1.06929 2009 1.03615 2010 0.9727 2011 0.88717 2012 0.86521 2013 0.83673 2014 0.82978 2015 0.85518 2016 0.86846 2017 0.87456