| Year | Value | | 2021 | 28.683067230701 | | 2020 | 40.980680196766 | | 2019 | 34.401166800729 | | 2018 | 32.884863547478 | | 2017 | 36.038926483645 | | 2016 | 29.644941440003 | | 2015 | 35.560714877407 | | 2014 | 38.800341178993 | | 2013 | 38.026605729501 | | 2012 | 39.200282633177 | | 2011 | 26.418137960493 | | 2010 | 27.920767219425 | | 2009 | 38.761886302092 | | 2008 | 40.30283006078 | | 2007 | 42.475420709148 | | 2006 | 42.54726696491 | | 2005 | 32.724388659265 | | 2004 | 40.594493647195 | | 2003 | 35.117900096042 | | 2002 | 28.225109617827 | | 2001 | 32.778950049159 | | 2000 | 38.539352405292 | | 1992 | 29.951946571103 | | 1991 | 42.39286354671 | | 1990 | 26.91149909693 |
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