| Year | Value | | 2021 | 44.825968728756 | | 2020 | 45.707965103104 | | 2019 | 46.589961477453 | | 2018 | 47.471957851801 | | 2017 | 48.35395422615 | | 2016 | 49.235950600498 | | 2015 | 50.117946974847 | | 2014 | 52.092125538183 | | 2013 | 54.066304101518 | | 2012 | 56.040482664854 | | 2011 | 58.014661228189 | | 2010 | 59.988839791525 | | 2009 | 60.097479039202 | | 2008 | 60.20611828688 | | 2007 | 60.314757534557 | | 2006 | 60.423396782234 | | 2005 | 60.532036029912 | | 2004 | 60.640675277589 | | 2003 | 60.749314525266 | | 2002 | 60.857953772944 | | 2001 | 60.966593020621 | | 2000 | 61.075232268298 | | 1999 | 61.202011103558 | | 1998 | 61.328789938817 | | 1997 | 61.455568774077 | | 1996 | 61.582347609336 | | 1995 | 61.709126444595 | | 1994 | 61.835905279855 | | 1993 | 61.962684115114 | | 1992 | 62.089462950374 | | 1991 | 62.216241785633 | | 1990 | 62.343020620893 |
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