Year Percent 1960 3.33606 1961 1.09579 1962 1.14315 1963 1.32253 1964 1.3822 1965 0.97629 1966 0.74787 1967 0.96173 1968 0.95673 1969 0.78234 1970 0.35576 1971 0.36426 1972 0.82672 1973 0.90811 1974 0.95979 1975 0.9936 1976 0.9978 1977 0.96387 1978 0.79406 1979 0.80219 1980 0.92327 1981 0.90787 1982 0.92028 1983 0.93769 1984 0.90459 1985 0.80359 1986 0.68107 1987 0.5642 1988 0.41446 1989 0.36166 1990 0.3924 1991 0.35468 1992 0.30668 1993 0.25445 1994 0.21101 1995 0.13572 1996 0.07607 1997 0.06546 1998 0.03575 1999 -0.0083 2000 -1.04434 2001 -0.02759 2002 -0.04632 2003 -0.06749 2004 -0.05851 2005 -0.04395 2006 -0.06337 2007 -0.05431 2008 0.01364 2009 0.06776 2010 -0.28561 2011 0.05377 2012 -0.00024 2013 -0.06036 2014 -0.07485 2015 -0.06664 2016 -0.04299 2017 0.01515