| Year | Value | | 2022 | 0.95932517563547 | | 2021 | 1.2122448994375 | | 2020 | 1.0261157002655 | | 2019 | 0.83406376924388 | | 2018 | 0.34112419563383 | | 2017 | 0.22140230446306 | | 2016 | 0.23010733150279 | | 2015 | 0.20205737954614 | | 2014 | 0.17417614523912 | | 2013 | 0.58791277183528 | | 2012 | 1.4289934173353 | | 2011 | 1.4117881545785 | | 2010 | 1.3551118711871 | | 2009 | 1.3152994262599 | | 2008 | 1.2046568480924 | | 2007 | 1.1794576492837 | | 2006 | 1.1834457647003 | | 2005 | 1.2282547954907 | | 2004 | 1.2642133530698 | | 2003 | 0.61213035461059 | | 2002 | 0.12480500839968 | | 2001 | 0.17654088390135 | | 2000 | 0.020749040431325 | | 1999 | 0.062260041442525 | | 1998 | 0.041528239799489 | | 1997 | 0.19749499688869 | | 1996 | 0.27088993435395 | | 1995 | 0.27162574159822 | | 1994 | 0.44034459914191 | | 1993 | 0.537324160615 | | 1992 | 1.1902372180362 | | 1991 | 1.8559013476664 | | 1990 | 1.8133361309261 | | 1989 | 1.937242152257 | | 1988 | 2.044733982763 | | 1987 | 1.9696458667986 | | 1986 | 1.985206354638 | | 1985 | 1.597516728231 | | 1984 | 1.2027636404041 | | 1983 | 1.3174438622971 | | 1982 | 1.4999966122336 | | 1981 | 1.8327972183208 | | 1980 | 2.3425791495138 | | 1979 | 3.4349124059716 | | 1978 | 4.3841486246182 | | 1977 | 4.4953033661569 | | 1976 | 4.5343959989522 | | 1975 | 4.5036053706944 | | 1974 | 2.7590249310635 | | 1973 | 0.72727593290799 | | 1972 | 0.63005742698562 | | 1971 | 0.685638613301 | | 1970 | 0.60381448010432 | | 1969 | 0.86896619092001 | | 1968 | 1.2647279065422 | | 1967 | 1.173555431651 | | 1966 | 0.77206595919231 | | 1965 | 0.41542550487687 | | 1964 | 0.39898493261947 | | 1963 | 0.5831982995933 | | 1962 | 0.64179187927915 | | 1961 | 0.59040761909448 |
|