| Year | Value | | 2020 | 0.40162150667103 | | 2019 | 0.40233304888387 | | 2018 | 0.4327800742808 | | 2017 | 0.42678676310693 | | 2016 | 0.42868353231138 | | 2015 | 0.43597140776728 | | 2014 | 0.43945939733214 | | 2013 | 0.45714084111333 | | 2012 | 0.49340181271251 | | 2011 | 0.50961877867984 | | 2010 | 0.56854475072459 | | 2009 | 0.57225015596162 | | 2008 | 0.52149559494938 | | 2007 | 0.53398253227054 | | 2006 | 0.54255609499261 | | 2005 | 2.6095596068902 | | 2004 | 0.096237961833949 | | 2003 | 0.66228355369313 | | 2002 | 0.67253117096693 | | 2001 | 0.65957687159244 | | 2000 | 0.69280188842288 | | 1999 | 0.69301855113088 | | 1998 | 0.66012830082975 | | 1997 | 0.66766842355502 | | 1996 | 0.69461707389123 | | 1995 | 0.84396078861416 | | 1994 | 1.0555080877631 | | 1993 | 0.93993013902104 | | 1992 | 0.84260355801584 | | 1991 | 0.60246737776074 |
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