| Year | Value | | 2021 | 46.412173122409 | | 2020 | 46.7251964699 | | 2019 | 47.007947811491 | | 2018 | 47.336107225514 | | 2017 | 47.568096848852 | | 2016 | 47.850008901549 | | 2015 | 48.246394872708 | | 2014 | 48.50889900557 | | 2013 | 48.771403138432 | | 2012 | 49.033907271294 | | 2011 | 49.296411404156 | | 2010 | 49.558915537018 | | 2009 | 49.840695338132 | | 2008 | 50.122475139246 | | 2007 | 50.40425494036 | | 2006 | 50.686034741474 | | 2005 | 50.967814542588 | | 2004 | 51.249594343702 | | 2003 | 51.531374144816 | | 2002 | 51.813153945929 | | 2001 | 52.094933747043 | | 2000 | 52.376713548157 | | 1999 | 52.655204862789 | | 1998 | 52.933696177421 | | 1997 | 53.212187492052 | | 1996 | 53.490678806684 | | 1995 | 53.769170121315 | | 1994 | 54.047661435947 | | 1993 | 54.326152750579 | | 1992 | 54.60464406521 | | 1991 | 54.883135379842 | | 1990 | 55.161626694473 |
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