Year % 1961 3.1078848748441743 1962 3.215345975872068 1963 3.374882242405081 1964 2.9516689997086836 1965 2.5659131262605226 1966 2.6494206288345064 1967 2.4062270318362655 1968 1.8639112466839627 1969 2.851773364219036 1970 2.514918207676119 1971 0.6219920275612227 1972 0.8839652181244488 1973 2.409693847438143 1974 1.6510659666039944 1975 -1.2815805405059535 1976 1.2667903810319 1977 0.5751010109735852 1978 1.8898082118975694 1979 4.03438928866804 1980 5.716362863586948 1981 8.59460069233457 1982 8.17720821228698 1983 6.618035468942819 1984 8.140906601926757 1985 6.563243833655473 1986 6.193869587084842 1987 5.587520283455384 1988 5.590302237069634 1989 6.6902646662395 1990 6.039749853491634 1991 4.915295961203665 1992 3.884294897661429 1993 3.545632163814808 1994 4.898541338048453 1995 6.594217971110523 1996 6.324285987508511 1997 6.603347423592494 1998 7.149945264678481 1999 6.487267351430267 2000 6.813792458514205 2001 4.567138943649962 2002 3.0732472423634976 2003 2.1065944904453655 2004 1.6076804608089537 2005 2.9608752131304388 2006 4.7278636699075784 2007 5.199863763119779 2008 3.1010422197860636 2009 2.6170776546007923 2010 2.01028262116756 2011 1.1628986522835818 2012 1.362463749765713 2013 1.522213388619228 2014 1.4825613905922823 2015 2.310514640598371 2016 2.5372322985710367 2017 2.2652963801397283 2018 2.5547498751073885 2019 3.544497456735186 2020 2.194566423461841 2021 -1.2762333113845887