| Year | Value | | 2022 | 20.889718778981 | | 2021 | 13.461262661941 | | 2020 | 4.6557199109396 | | 2019 | 16.722006238625 | | 2018 | 12.33872999149 | | 2017 | 14.310950566258 | | 2016 | 15.529237431618 | | 2015 | 14.988400021813 | | 2014 | 10.710053813636 | | 2013 | 6.9821501651854 | | 2012 | 5.7508468136378 | | 2011 | -1.2401468087833 | | 2010 | 4.6486192757365 | | 2009 | 11.174913747775 | | 2008 | 15.345106655682 | | 2007 | 2.9173640585014 | | 2006 | 13.104232802859 | | 2005 | -1.6529531543651 | | 2004 | 17.248333033232 | | 2003 | 14.646461765111 | | 2002 | 12.207159607822 | | 2001 | 19.189308306992 | | 2000 | 23.714642771197 | | 1999 | 20.650129701686 | | 1998 | 27.084870848709 | | 1997 | 24.314369073669 | | 1996 | 24.842105263158 | | 1995 | 30.956006768189 |
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