| Year | Value | | 2024 | 1.0744792096203 | | 2023 | 1.12092864341 | | 2022 | 1.0682929553062 | | 2021 | 1.0964282539596 | | 2020 | 1.4363216732697 | | 2019 | 1.7861550772439 | | 2018 | 1.839137848611 | | 2017 | 1.4514772616919 | | 2016 | 0.99054854932691 | | 2015 | 0.8649423767627 | | 2014 | 0.89271156392637 | | 2013 | 0.94870932875153 | | 2012 | 1.0029078265534 | | 2011 | 1.0713372766627 | | 2010 | 1.1359683636363 | | 2009 | 1.1649137009438 | | 2008 | 1.2033915480646 | | 2007 | 1.266890996292 | | 2006 | 1.3254299099262 | | 2005 | 1.4002642115634 | | 2004 | 1.4688372553323 | | 2003 | 1.5081090586904 | | 2002 | 1.5379228224816 | | 2001 | 1.5719468839022 | | 2000 | 1.6379827495052 | | 1999 | 1.738335788822 | | 1998 | 1.791494490607 | | 1997 | 1.7895806699384 | | 1996 | 1.8212946011351 | | 1995 | 1.9096370992151 | | 1994 | 1.972028872009 | | 1993 | 1.9967865587928 | | 1992 | 1.9809486208433 | | 1991 | 2.0089740634751 | | 1990 | 2.0674288212953 | | 1989 | 2.053125108652 | | 1988 | 2.0479608898344 | | 1987 | 2.0549567103333 | | 1986 | 2.0648813560735 | | 1985 | 2.1612565123953 | | 1984 | 2.3116234177744 | | 1983 | 2.3492244738975 | | 1982 | 2.3129449963769 | | 1981 | 2.3052696737271 | | 1980 | 2.2816587842591 | | 1979 | 2.2403719682127 | | 1978 | 2.2570871720033 | | 1977 | 2.2162916240851 | | 1976 | 2.1785962370925 | | 1975 | 2.2140180600269 |
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