| Year | Value | | 2022 | 1.2577843370441 | | 2021 | 1.5398824689606 | | 2020 | 1.7198008562205 | | 2019 | 1.5816846764634 | | 2018 | 1.549487295357 | | 2017 | 1.8113827695781 | | 2016 | 1.4475458041817 | | 2015 | 1.1850256085491 | | 2014 | 1.1448183963 | | 2013 | 1.6040471794898 | | 2012 | 1.619804647871 | | 2011 | 1.4624342299704 | | 2010 | 1.8716225658957 | | 2006 | 1.2826192101326 | | 2005 | 1.2486821692997 | | 2004 | 1.6131661692941 | | 2003 | 1.668327932894 | | 2002 | 1.783170276821 | | 2001 | 1.7939520982173 | | 2000 | 1.8014522476581 | | 1986 | 3.9959277169763 | | 1985 | 2.8590469843385 | | 1984 | 2.2554941524226 | | 1983 | 2.5535866284918 | | 1982 | 2.4476406762554 | | 1981 | 2.2868032396379 | | 1980 | 1.6036275160363 | | 1979 | 1.877133105802 | | 1977 | 1.0297015357867 | | 1976 | 0.66847448199138 | | 1975 | 0.78070934256055 | | 1974 | 0.67958030669895 | | 1973 | 1.3035381750466 | | 1972 | 1.5502304147465 | | 1971 | 1.4405328258801 | | 1970 | 1.4324019145471 | | 1969 | 1.3675956966322 | | 1968 | 1.0150888847493 | | 1967 | 1.1077844311377 |
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