| Year | Value | | 2021 | 15.033939301447 | | 2020 | 15.537189081063 | | 2019 | 16.574117124678 | | 2018 | 16.269479472021 | | 2017 | 15.276855367551 | | 2016 | 15.476934977149 | | 2015 | 15.322031844754 | | 2014 | 13.785331937658 | | 2013 | 12.436394915496 | | 2012 | 14.28237598568 | | 2011 | 14.565816432944 | | 2010 | 14.772329714082 | | 2009 | 47.996911612096 | | 2008 | 48.265619011115 | | 2007 | 49.230201037671 | | 2006 | 49.881027918782 | | 2005 | 48.141974703402 | | 2004 | 50.152673063665 | | 2003 | 50.500506136425 | | 1995 | 52.62312633833 | | 1994 | 45.571062375392 | | 1993 | 48.547008547009 | | 1992 | 45.940921297253 | | 1991 | 44.808092829515 | | 1990 | 50.138185168125 |
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