| Year | Value | | 2024 | 52.333108818295 | | 2023 | 52.383460269012 | | 2022 | 52.438295068484 | | 2021 | 52.488559688704 | | 2020 | 52.530168792989 | | 2019 | 52.568479785177 | | 2018 | 52.605715193344 | | 2017 | 52.640570297402 | | 2016 | 52.673610545103 | | 2015 | 52.704126317547 | | 2014 | 52.732119511594 | | 2013 | 52.761965001806 | | 2012 | 52.728474331857 | | 2011 | 52.665139388076 | | 2010 | 52.644789106047 | | 2009 | 52.6312297465 | | 2008 | 52.616761130167 | | 2007 | 52.599316560422 | | 2006 | 52.613084820381 | | 2005 | 52.607756633573 | | 2004 | 52.552035048653 | | 2003 | 52.516995546716 | | 2002 | 52.505006555036 | | 2001 | 52.48108884295 | | 2000 | 52.413893141261 | | 1999 | 52.352874682457 | | 1998 | 52.367905735717 | | 1997 | 52.422129868631 | | 1996 | 52.464650043972 | | 1995 | 52.476623519456 | | 1994 | 52.39343748471 | | 1993 | 52.198993249535 | | 1992 | 51.7830315512 | | 1991 | 51.466960248693 | | 1990 | 51.445831338223 | | 1989 | 51.422112386094 | | 1988 | 51.367303712141 | | 1987 | 51.226891545534 | | 1986 | 51.106948484828 | | 1985 | 51.067946322777 | | 1984 | 51.034691344372 | | 1983 | 51.002790179398 | | 1982 | 51.056628516195 | | 1981 | 51.163118509318 | | 1980 | 51.97002600229 | | 1979 | 52.669935737294 | | 1978 | 52.150177846208 | | 1977 | 51.591910893117 | | 1976 | 51.347074901258 |
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