| Year | Value | | 2021 | 43.290146628465 | | 2020 | 43.734030980434 | | 2019 | 44.175884786272 | | 2018 | 44.61974873602 | | 2017 | 45.060160857909 | | 2016 | 45.501899568001 | | 2015 | 45.924603417652 | | 2014 | 46.3682121639 | | 2013 | 46.811820910149 | | 2012 | 47.250365153487 | | 2011 | 47.683705551899 | | 2010 | 48.129381869393 | | 2009 | 48.651019439767 | | 2008 | 49.174851142643 | | 2007 | 49.683457277513 | | 2006 | 50.211706734816 | | 2005 | 50.744696645035 | | 2004 | 51.264525114015 | | 2003 | 51.779503932429 | | 2002 | 52.30389570646 | | 2001 | 52.828287480491 | | 2000 | 53.352679254521 | | 1999 | 54.01834164703 | | 1998 | 54.684004039539 | | 1997 | 55.349666432047 | | 1996 | 56.015328824556 | | 1995 | 56.680991217064 | | 1994 | 57.346653609572 | | 1993 | 58.012316002081 | | 1992 | 58.67797839459 | | 1991 | 59.343640787098 | | 1990 | 60.009303179606 |
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