Year Percent 1960 -0.2807 1961 -0.14859 1962 0.41163 1963 0.58361 1964 0.48608 1965 0.37431 1966 0.39888 1967 0.4714 1968 0.45033 1969 0.5848 1970 0.83533 1971 1.1699 1972 1.4862 1973 1.60388 1974 1.65668 1975 1.64535 1976 1.50915 1977 1.35426 1978 1.41881 1979 1.33229 1980 1.15082 1981 1.17103 1982 0.94542 1983 0.70894 1984 0.61971 1985 0.16007 1986 0.04544 1987 0.01037 1988 -0.42769 1989 -0.39625 1990 0.08441 1991 0.57493 1992 0.68226 1993 0.49984 1994 0.39419 1995 0.5127 1996 0.79127 1997 1.00281 1998 1.04308 1999 1.1273 2000 1.33304 2001 1.59215 2002 1.68515 2003 1.62895 2004 1.82831 2005 2.1787 2006 2.69601 2007 2.89096 2008 2.03871 2009 1.01566 2010 0.54488 2011 0.43607 2012 0.42374 2013 0.52656 2014 0.731 2015 0.94485 2016 1.12883 2017 1.21798