| Year | Value | | 2022 | 1.1863043287208 | | 2021 | 0.97996576779414 | | 2020 | 1.1674681358797 | | 2019 | 1.255654723075 | | 2018 | 1.4374987507927 | | 2017 | 1.300004050559 | | 2016 | 1.4545326360044 | | 2015 | 1.7852542034071 | | 2014 | 1.6618695574344 | | 2013 | 1.4344290864882 | | 2012 | 1.3936669272869 | | 2011 | 1.2623324206453 | | 2010 | 1.3825927651752 | | 2009 | 1.7316353471036 | | 2008 | 2.0800878769722 | | 2007 | 2.0637069922309 | | 2006 | 1.7439454502704 | | 2005 | 1.8483229444939 | | 2004 | 1.5808996044652 | | 1999 | 1.6483184604395 | | 1997 | 1.0076610376551 | | 1996 | 1.0518095531385 | | 1995 | 1.451688414195 | | 1994 | 1.7192453856092 | | 1993 | 1.429398242593 | | 1992 | 2.7050497634892 | | 1991 | 2.3374458851178 | | 1990 | 3.4108250888458 | | 1989 | 4.1952694033475 | | 1988 | 2.3883440814369 | | 1987 | 3.2206851919265 | | 1986 | 3.6641221374046 | | 1985 | 2.3614587310341 | | 1984 | 3.0014195903468 |
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