| Year | Value | | 2022 | 11.517693792887 | | 2021 | 11.935638796872 | | 2020 | 12.217610875534 | | 2019 | 12.937793184876 | | 2018 | 14.732136534047 | | 2017 | 15.538093493571 | | 2016 | 15.689636896051 | | 2015 | 20.476368301914 | | 2014 | 26.819348554665 | | 2013 | 28.455454281522 | | 2012 | 28.410936007453 | | 2011 | 28.410184450436 | | 2010 | 33.616291350227 | | 2009 | 51.820861716364 | | 2008 | 41.517052735531 | | 2007 | 42.069921558581 | | 2006 | 57.415319076008 | | 2005 | 47.197058715902 | | 2004 | 44.214495123354 | | 2003 | 51.195533438524 | | 2002 | 49.573085893317 | | 2001 | 50.152420436532 | | 2000 | 47.616761801403 | | 1999 | 50.218213998472 | | 1998 | 50.985629025465 | | 1997 | 52.499605021693 | | 1996 | 51.958394279213 | | 1995 | 51.37861466039 | | 1994 | 54.974302496329 | | 1993 | 55.924369747899 | | 1992 | 55.62734472697 | | 1991 | 62.17299080839 | | 1990 | 65.823650034176 |
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