Year Percent 1960 2.26691 1961 1.98974 1962 2.44064 1963 1.91782 1964 1.96235 1965 1.95972 1966 2.28318 1967 1.26228 1968 1.76416 1969 2.09302 1970 1.97019 1971 3.38029 1972 1.83815 1973 1.52882 1974 2.53122 1975 1.23119 1976 1.00266 1977 1.12667 1978 1.16289 1979 1.08064 1980 1.21894 1981 1.58685 1982 1.66754 1983 1.25055 1984 1.13222 1985 1.36735 1986 1.63899 1987 1.52099 1988 1.63621 1989 1.69257 1990 1.47998 1991 1.27458 1992 1.21339 1993 0.97834 1994 1.05851 1995 1.20802 1996 1.31382 1997 1.11873 1998 1.04224 1999 1.14251 2000 1.19227 2001 1.34836 2002 1.22056 2003 1.234 2004 1.15935 2005 1.31979 2006 1.47523 2007 0.62468 2008 2.00402 2009 2.06105 2010 1.55549 2011 1.38953 2012 1.78545 2013 1.75834 2014 1.53588 2015 1.46406 2016 1.49821 2017 1.59039