| Year | Value | | 2022 | 15.325258926437 | | 2021 | 3.2977443529951 | | 2020 | 1.6724409685576 | | 2019 | 3.1037294479678 | | 2018 | 2.8145447382483 | | 2017 | 2.0615961944314 | | 2016 | 0.79864988645371 | | 2015 | 0.10463326100839 | | 2014 | -1.4181838026484 | | 2013 | 0.890093540913 | | 2012 | 2.9545682983102 | | 2011 | 4.2199034660187 | | 2010 | 2.4389906050411 | | 2009 | 2.7532022391482 | | 2008 | 12.348719599402 | | 2007 | 8.402534190059 | | 2006 | 7.2615946276994 | | 2005 | 5.038838071119 | | 2004 | 6.1471307424627 | | 2003 | 2.3486416958276 | | 2002 | 5.8101436572182 | | 2001 | 7.3609392723184 | | 2000 | 10.316262128999 | | 1999 | 2.5730428189021 | | 1998 | 18.672204442064 | | 1997 | 1,058.3735592197 | | 1996 | 121.60754244925 | | 1995 | 62.054833683799 | | 1994 | 96.05733826865 | | 1993 | 72.878791386633 | | 1992 | 91.29793272693 | | 1991 | 338.44911147011 | | 1990 | 23.8 | | 1989 | 6.3888888888888 | | 1988 | 2.3696682464455 | | 1987 | 2.7263875365141 | | 1986 | 2.6999999999999 |
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