| Year | Value | | 2021 | 48.361944868121 | | 2020 | 49.071780365472 | | 2019 | 49.394296409251 | | 2018 | 49.716817779208 | | 2017 | 50.039333822987 | | 2016 | 50.743454526958 | | 2015 | 50.613549050635 | | 2014 | 51.106891594706 | | 2013 | 51.600234138776 | | 2012 | 52.093576682846 | | 2011 | 52.586919226916 | | 2010 | 53.080261770986 | | 2009 | 53.166588460623 | | 2008 | 53.252915150259 | | 2007 | 53.339241839896 | | 2006 | 53.425568529533 | | 2005 | 53.51189521917 | | 2004 | 53.598221908806 | | 2003 | 53.684548598443 | | 2002 | 53.77087528808 | | 2001 | 53.857201977716 | | 2000 | 53.943528667353 | | 1999 | 56.860347654245 | | 1998 | 57.813388386869 | | 1997 | 58.766429119493 | | 1996 | 59.719469852117 | | 1995 | 60.672510584741 | | 1994 | 61.625551317366 | | 1993 | 62.57859204999 | | 1992 | 63.531632782614 | | 1991 | 64.484673515238 | | 1990 | 65.437714247862 |
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