| Year | Value | | 2022 | 1.8505037841192 | | 2021 | 0.95387818351947 | | 2020 | 1.0291105027734 | | 2019 | 1.367626953638 | | 2018 | 1.2388754525895 | | 2017 | 1.08867556062 | | 2016 | 1.1288340639943 | | 2015 | 0.94484530747473 | | 2014 | 0.73100137658577 | | 2013 | 0.52655615885565 | | 2012 | 0.4237438032978 | | 2011 | 0.43607243925843 | | 2010 | 0.54488438407901 | | 2009 | 1.0156632759234 | | 2008 | 2.038708011172 | | 2007 | 2.8909600046416 | | 2006 | 2.6960056435958 | | 2005 | 2.1787030135563 | | 2004 | 1.828313817909 | | 2003 | 1.6289509619302 | | 2002 | 1.6851488573028 | | 2001 | 1.592151490393 | | 2000 | 1.3330426658671 | | 1999 | 1.1272995564947 | | 1998 | 1.0430768361115 | | 1997 | 1.0028147352186 | | 1996 | 0.79127134699446 | | 1995 | 0.51269505531852 | | 1994 | 0.39418763865374 | | 1993 | 0.49984048711299 | | 1992 | 0.6822567779864 | | 1991 | 0.5749277812058 | | 1990 | 0.084413020673799 | | 1989 | 0.39625075191935 | | 1988 | 0.42768606365056 | | 1987 | 0.010367602128396 | | 1986 | 0.045438028454889 | | 1985 | 0.16007346599323 | | 1984 | 0.6197074705094 | | 1983 | 0.70893899346641 | | 1982 | 0.9454154697589 | | 1981 | 1.1710349672906 | | 1980 | 1.1508183384872 | | 1979 | 1.3322888157587 | | 1978 | 1.41880679291 | | 1977 | 1.3542632496532 | | 1976 | 1.5091455751547 | | 1975 | 1.645353655741 | | 1974 | 1.656675285169 | | 1973 | 1.6038757608598 | | 1972 | 1.4862022795067 | | 1971 | 1.1698988758837 | | 1970 | 0.83533313112375 | | 1969 | 0.58479698824231 | | 1968 | 0.45032733373721 | | 1967 | 0.47140169315657 | | 1966 | 0.39888365612327 | | 1965 | 0.37431383311171 | | 1964 | 0.48608292658753 | | 1963 | 0.58361478429751 | | 1962 | 0.41162863198558 | | 1961 | 0.14859369442076 |
|