| Year | Value | | 2020 | 0.832549979489 | | 2019 | 0.81812184511763 | | 2018 | 0.78922623508268 | | 2017 | 0.81416649704865 | | 2016 | 0.76880271790066 | | 2015 | 0.75767798397042 | | 2014 | 0.74963589113859 | | 2013 | 0.75725995941087 | | 2012 | 0.74138196422444 | | 2011 | 0.73860569447488 | | 2010 | 0.72234981891741 | | 2009 | 0.72249389838636 | | 2008 | 0.60375940858412 | | 2007 | 0.60702203085291 | | 2006 | 0.61017238725879 | | 2005 | 0.81383961391449 | | 2004 | 1.6226324778004 | | 2003 | 1.2703955930788 | | 2002 | 1.3491708731725 | | 2001 | 1.6596339677284 | | 2000 | 5.3155514150208 | | 1999 | 6.0975134198471 | | 1998 | 6.2052554184146 | | 1997 | 6.3642889387178 | | 1996 | 17.598577228681 | | 1995 | 7.5303177139265 | | 1994 | 5.6900299295574 | | 1992 | 4.1100084871675 |
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