| Year | Value | | 2022 | 0.3604470561234 | | 2021 | -1.0251787078419 | | 2020 | -1.6749855975126 | | 2019 | -2.9049957453773 | | 2018 | -2.4435432248287 | | 2017 | 0.58080678438909 | | 2016 | 0.69118578424476 | | 2015 | 1.1081849953109 | | 2014 | 1.1835201663898 | | 2013 | 1.2396200737455 | | 2012 | 1.2781079685037 | | 2011 | 1.3185771872378 | | 2010 | 1.3573498146076 | | 2009 | 1.4008295831881 | | 2008 | 1.4740399816542 | | 2007 | 1.5487692066186 | | 2006 | 1.6116734254595 | | 2005 | 1.6707149263617 | | 2004 | 1.7108932251121 | | 2003 | 1.7651559616598 | | 2002 | 1.7953712217765 | | 2001 | 1.8353505529085 | | 2000 | 1.9042706267462 | | 1999 | 1.9513296620145 | | 1998 | 2.0036947735796 | | 1997 | 2.0410897459825 | | 1996 | 2.0807835941324 | | 1995 | 2.1325290680119 | | 1994 | 2.189766956399 | | 1993 | 2.2528306649193 | | 1992 | 2.3176484689717 | | 1991 | 2.3796678491915 | | 1990 | 2.4358738881523 | | 1989 | 2.4926242047606 | | 1988 | 2.543214426222 | | 1987 | 2.5853283737138 | | 1986 | 2.6009787196967 | | 1985 | 2.6143999160348 | | 1984 | 2.6516824472836 | | 1983 | 2.6884688457015 | | 1982 | 2.7326008490962 | | 1981 | 2.7748859244153 | | 1980 | 2.8130824459945 | | 1979 | 2.8502812968161 | | 1978 | 2.877649285973 | | 1977 | 2.8997182710744 | | 1976 | 2.9148554395058 | | 1975 | 2.9276549216453 | | 1974 | 2.9455017601864 | | 1973 | 2.9666203666782 | | 1972 | 2.9954912028704 | | 1971 | 3.0373675040139 | | 1970 | 3.0774809684776 | | 1969 | 3.1240427635301 | | 1968 | 3.1776318273439 | | 1967 | 3.2255428327015 | | 1966 | 3.2750771978793 | | 1965 | 3.3246901903438 | | 1964 | 3.3791416268534 | | 1963 | 3.4343826532184 | | 1962 | 3.498615807646 | | 1961 | 3.5665216933933 |
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