| Year | Value | | 2020 | 1.1303556998348 | | 2019 | 1.138847313314 | | 2018 | 1.1316564963129 | | 2017 | 1.1455088249496 | | 2016 | 1.1414260385056 | | 2015 | 1.1359503533592 | | 2014 | 1.1348694861307 | | 2013 | 1.1430743480456 | | 2012 | 1.1104271916602 | | 2011 | 1.1693029143572 | | 2010 | 1.0690980961462 | | 2009 | 1.0644027871035 | | 2008 | 1.0807023600152 | | 2007 | 1.0919660289368 | | 2006 | 1.1121907599933 | | 2005 | 1.1212388661447 | | 2004 | 1.1315922710465 | | 2003 | 1.1701441339828 | | 2002 | 1.1606965220712 | | 2001 | 1.1492639973207 | | 2000 | 1.18881067197 | | 1999 | 1.0984377360039 | | 1998 | 1.1018499856672 | | 1997 | 0.99258392540081 | | 1996 | 1.1816274616588 | | 1995 | 1.2930564743107 | | 1994 | 0.91437358063208 | | 1993 | 0.94907501540397 | | 1992 | 0.93039540983014 | | 1991 | 0.95231518927248 | | 1990 | 0.97615498278139 |
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