Year | Value | 2021 | 1.8346189945645 | 2020 | 1.8239033263749 | 2019 | 1.8228120256585 | 2018 | 1.8520371604003 | 2017 | 1.8655017059789 | 2016 | 1.9295386707521 | 2015 | 1.9350017857913 | 2014 | 1.9193602836756 | 2013 | 1.8736879215417 | 2012 | 1.858359148233 | 2011 | 1.801654804349 | 2010 | 1.8120725102871 | 2009 | 1.8151869257046 | 2008 | 1.7997571865511 | 2007 | 1.7245137191462 | 2006 | 1.660981551606 | 2005 | 1.6295688926903 | 2004 | 1.6467378982674 | 2003 | 1.6104096407221 | 2002 | 1.6089934895712 | 2001 | 1.6147920874672 | 2000 | 1.6191566792756 | 1999 | 1.6256662649121 | 1998 | 1.684573506414 | 1997 | 1.7287176771057 | 1996 | 1.794945027787 | 1995 | 1.8596851452064 | 1994 | 1.925825059803 | 1993 | 1.9721545349567 | 1992 | 2.0899375408368 | 1991 | 2.2190624341898 | 1990 | 2.3084160328674 | 1989 | 2.4149901706135 | 1988 | 2.5068447403019 | 1987 | 2.5732058287626 | 1986 | 2.5788372579669 | 1985 | 2.5526974386756 | 1984 | 2.5820851397831 | 1983 | 2.597209545051 | 1982 | 2.5661479425602 | 1981 | 2.5188580684251 | 1980 | 2.5349578891628 | 1979 | 2.5624357776255 | 1978 | 2.581779796604 | 1977 | 2.6124477307771 | 1976 | 2.654394787491 | 1975 | 2.6795732851343 | 1974 | 2.714661003345 | 1973 | 2.7139862365537 | 1972 | 2.7457110549624 | 1971 | 2.7615482561368 | 1970 | 2.7565663320666 | 1969 | 2.7678495921635 | 1968 | 2.8034685145945 | 1967 | 2.842511890598 | 1966 | 2.7853836857367 | 1965 | 2.8257571243887 | 1964 | 2.8573541581076 | 1963 | 2.9319843733757 | 1962 | 2.9877781964756 | 1961 | 3.048090885325 | 1960 | 3.1036831937659 |
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