| Year | Value | | 2022 | 1.2366559125867 | | 2021 | 1.2672944647353 | | 2020 | 1.4008356862371 | | 2019 | 1.2845122436692 | | 2018 | 1.3176781061648 | | 2017 | 1.3518964646571 | | 2016 | 1.1641615671909 | | 2015 | 1.1527093744552 | | 2014 | 0.98992529943887 | | 2013 | 1.002367200474 | | 2012 | 1.118404598071 | | 2011 | 1.1932918954964 | | 2010 | 1.1943383383912 | | 2009 | 1.3775556310752 | | 2008 | 1.2455183667755 | | 2007 | 1.185790229967 | | 2006 | 1.1225247293205 | | 2005 | 1.1071054242081 | | 2004 | 1.1041893914269 | | 2003 | 1.1119373068834 | | 2002 | 1.1168691473694 | | 2001 | 1.1333562828133 | | 2000 | 1.1143498021375 | | 1999 | 1.2417030641026 | | 1998 | 1.2562939015687 | | 1997 | 1.2462432015117 | | 1996 | 1.4037525810645 | | 1995 | 1.5540900711478 | | 1994 | 1.6966802573186 | | 1993 | 1.8217535039275 | | 1992 | 1.8616876998629 | | 1991 | 1.8954443385806 | | 1990 | 1.9587937422142 | | 1989 | 1.9346143086504 | | 1988 | 1.9867671189084 | | 1987 | 2.0625763710106 | | 1986 | 2.1091971178891 | | 1985 | 2.0973762337507 | | 1984 | 2.1171888554257 | | 1983 | 2.0811962487785 | | 1982 | 1.954343585383 | | 1981 | 1.7099156381512 | | 1980 | 1.7644486147778 | | 1979 | 1.7112459179403 | | 1978 | 1.8488874006134 | | 1977 | 1.8057636000778 | | 1976 | 1.7659279778393 | | 1975 | 1.8635418526561 | | 1974 | 1.7838130850829 | | 1973 | 1.8326018176743 | | 1972 | 2.0118184382193 | | 1971 | 2.1314856393949 | | 1970 | 2.1889796959381 | | 1969 | 2.2737846704444 | | 1968 | 2.5436418804429 | | 1967 | 2.7479267697782 | | 1966 | 2.6832824215496 | | 1965 | 2.9302606594165 | | 1964 | 3.4020628365906 | | 1963 | 3.620650111549 | | 1962 | 3.9992163886712 | | 1961 | 4.1283122434605 | | 1960 | 4.1852565402555 |
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