Year Percent 1960 1.4695 1961 1.1106 1962 1.11146 1963 1.11053 1964 1.1111 1965 1.11073 1966 0.56882 1967 0.5695 1968 0.56938 1969 0.56924 1970 0.56908 1971 0.57425 1972 0.57325 1973 0.5745 1974 0.57347 1975 0.57392 1976 0.70319 1977 0.70268 1978 0.70289 1979 0.70305 1980 0.70966 1981 0.6675 1982 0.62829 1983 0.59825 1984 0.75735 1985 0.77669 1986 0.71757 1987 0.69738 1988 0.6483 1989 0.5866 1990 0.38579 1991 0.22363 1992 0.04372 1993 -0.11372 1994 -0.12397 1995 0.02678 1996 -0.14547 1997 -0.16532 1998 -0.16551 1999 -0.30948 2000 -0.42057 2001 -0.42415 2002 -0.46006 2003 -0.45372 2004 -0.40261 2005 -0.38147 2006 -0.32732 2007 -0.17102 2008 -0.04394 2009 0.03011 2010 0.04489 2011 0.07797 2012 0.1683 2013 0.21292 2014 0.2177 2015 0.19256 2016 0.17024 2017 0.1057