| Year | Value | | 2022 | 3.6822503060422 | | 2021 | 1.7334138845059 | | 2020 | 1.9403199660718 | | 2019 | 0.39052206916553 | | 2018 | 1.0250517929021 | | 2017 | -1.2605056462896 | | 2016 | 0.27869326575308 | | 2015 | 0.48834742074352 | | 2014 | 0.20710873171982 | | 2013 | 0.38920505312363 | | 2012 | 0.11176626140031 | | 2011 | 0.13791156316954 | | 2010 | 0.35686913201756 | | 2009 | 1.0357177427161 | | 2008 | 2.0849802371541 | | 2007 | 0.9677741195251 | | 2006 | 0.15988807834512 | | 2005 | 1.2444371188396 | | 2004 | 0.81422399468261 | | 2003 | 0.29999999999997 | | 2002 | -2.3149724245932 | | 2001 | 0.59589041095899 | | 2000 | 1.5581524763495 | | 1999 | 0.41562759767245 | | 1998 | 0.4413793103449 | | 1997 | 1.7115600448933 | | 1996 | 1.9961365099808 | | 1995 | 5.9666413949961 | | 1994 | 2.4625184494679 | | 1993 | 4.2517006802721 | | 1992 | 1.2795275590552 | | 1991 | 1.6 | | 1990 | 2.1386629316379 | | 1989 | 1.3043003710982 | | 1988 | 1.192842942346 | | 1987 | 1.2468549063458 | | 1986 | 1.7812428864106 | | 1985 | 2.3532152842493 | | 1984 | 3.0739673390973 | | 1983 | 1.1661807580175 | | 1982 | 6.3565891472869 | | 1981 | 9.1370558375634 |
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