Year Percent 1960 1.65791 1961 1.46301 1962 1.287 1963 1.14835 1964 1.06598 1965 1.05357 1966 1.02647 1967 1.00692 1968 0.99463 1969 1.01388 1970 1.04019 1971 1.08637 1972 1.11255 1973 1.13347 1974 1.11759 1975 1.09687 1976 1.07152 1977 1.03763 1978 1.00265 1979 0.96559 1980 0.91457 1981 0.86585 1982 0.81048 1983 0.76028 1984 0.73334 1985 0.70599 1986 0.68773 1987 0.66132 1988 0.60255 1989 0.51306 1990 0.39238 1991 0.28702 1992 0.17515 1993 0.08237 1994 0.03422 1995 -0.00647 1996 -0.04348 1997 -0.06572 1998 -0.07595 1999 -0.03892 2000 0.01668 2001 0.08338 2002 0.14621 2003 0.18846 2004 0.19271 2005 0.17027 2006 0.14978 2007 0.12847 2008 0.10815 2009 0.08058 2010 0.05673 2011 0.02378 2012 -0.01189 2013 -0.00732 2014 0.03384 2015 0.08957 2016 0.17161 2017 0.23139