| Year | Value | | 2022 | 0.20978771050677 | | 2021 | 0.26462266358369 | | 2020 | 0.42812577712617 | | 2019 | 0.53272665424062 | | 2018 | 0.61237261506784 | | 2017 | 0.71021537709394 | | 2016 | 0.7066809497057 | | 2015 | 0.71435792973642 | | 2014 | 0.74992164816787 | | 2013 | 0.77983574699945 | | 2012 | 0.7989531071533 | | 2011 | 0.71433848317616 | | 2010 | 0.68486946246864 | | 2009 | 0.6998257373086 | | 2008 | 0.72817413141533 | | 2007 | 0.73307700209115 | | 2006 | 0.74503778106872 | | 2005 | 0.74959488523704 | | 2004 | 0.76364019846986 | | 2003 | 0.79849636217398 | | 2002 | 0.84392178220969 | | 2001 | 0.89746057187637 | | 2000 | 0.94409698205007 | | 1999 | 1.0112496943584 | | 1998 | 1.1029051693151 | | 1997 | 1.1570582892303 | | 1996 | 1.1927578257515 | | 1995 | 1.2171480875341 | | 1994 | 1.2652571496991 | | 1993 | 1.2913340930248 | | 1992 | 1.3471525090132 | | 1991 | 1.4495506193926 | | 1990 | 1.5125034804682 | | 1989 | 1.5650926634976 | | 1988 | 1.620760001572 | | 1987 | 1.6289925248714 | | 1986 | 1.5668991202497 | | 1985 | 1.5099760739957 | | 1984 | 1.5028437270362 | | 1983 | 1.6071684069358 | | 1982 | 1.6377461334166 | | 1981 | 1.5192465478462 | | 1980 | 1.4925387324733 | | 1979 | 1.5532087486412 | | 1978 | 1.5539456565453 | | 1977 | 1.5618412490839 | | 1976 | 1.6766539918821 | | 1975 | 1.8551076671416 | | 1974 | 2.0953281260892 | | 1973 | 2.2517084581107 | | 1972 | 2.3798200299477 | | 1971 | 2.6575393763967 | | 1970 | 2.592244413657 | | 1969 | 2.5875220552062 | | 1968 | 2.4853009078374 | | 1967 | 2.4300110956293 | | 1966 | 2.5771780281645 | | 1965 | 2.3503168929536 | | 1964 | 2.3420298159026 | | 1963 | 2.4347574426823 | | 1962 | 1.3774523695725 | | 1961 | 0.17917576271833 |
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