| Year | Value | | 2022 | 0.99460714916237 | | 2021 | 1.7022882253456 | | 2020 | 1.7618912950745 | | 2019 | 1.75749125737 | | 2018 | 1.5801470865614 | | 2017 | 1.7721827128786 | | 2016 | 1.1006029897986 | | 2015 | 0.17437769036746 | | 2014 | 0.35527494218565 | | 2013 | 0.49726187588756 | | 2012 | 0.63003457452458 | | 2011 | -1.3400535537482 | | 2010 | -3.2099941868897 | | 2009 | -2.939367223021 | | 2008 | -2.7403593878336 | | 2007 | -2.592496934144 | | 2006 | 0.49360600574085 | | 2005 | 3.6914352725258 | | 2004 | 4.0127367134456 | | 2003 | 4.2256694355319 | | 2002 | 4.3693715013548 | | 2001 | 2.573377664894 | | 2000 | 0.67096007375839 | | 1999 | 0.71690373612242 | | 1998 | 0.77617662594036 | | 1997 | 0.83056311158388 | | 1996 | 1.9186108885048 | | 1995 | 3.0510978020666 | | 1994 | 3.1302215364265 | | 1993 | 3.2174126721942 | | 1992 | 3.2810771665917 | | 1991 | 3.4222581362485 | | 1990 | 3.6693341596699 | | 1989 | 3.9198249763764 | | 1988 | 4.1511166034972 | | 1987 | 4.3550425526621 | | 1986 | 4.0178083905678 | | 1985 | 3.7869393038399 | | 1984 | 4.2348332042207 | | 1983 | 4.642108898892 | | 1982 | 4.2633962102393 | | 1981 | 3.7911920659693 | | 1980 | 4.2126280936272 | | 1979 | 4.7013873807192 | | 1978 | 5.1173735720455 | | 1977 | 5.4957971534799 | | 1976 | 5.8118717996646 | | 1975 | 6.1052082918895 | | 1974 | 6.3915710086764 | | 1973 | 6.613314515933 | | 1972 | 6.8423657206197 | | 1971 | 7.1031744911257 | | 1970 | 7.3697490141398 | | 1969 | 7.7160529838574 | | 1968 | 8.1326784084067 | | 1967 | 7.9206812820639 | | 1966 | 6.9970544751771 | | 1965 | 6.6531215254282 | | 1964 | 6.9415115296797 | | 1963 | 7.223197558921 | | 1962 | 7.5212072110052 | | 1961 | 7.8681392449306 |
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