| Year | Value | | 2022 | 9.6968189908107 | | 2021 | 2.1803227808815 | | 2020 | 2.5431468568165 | | 2019 | 1.7601115119294 | | 2018 | 0.46098564246428 | | 2017 | 1.3181531484778 | | 2016 | 0.83728494255743 | | 2015 | 0.13521193363526 | | 2014 | -1.090255074469 | | 2013 | 0.71024548669527 | | 2012 | 1.4182287117784 | | 2011 | 3.4032282978697 | | 2010 | 1.2286811967334 | | 2009 | -2.2480214785534 | | 2008 | 7.347202365784 | | 2007 | 5.8533042846769 | | 2006 | 2.1122858387711 | | 2005 | 1.711333258555 | | 2004 | 0.51478178102298 | | 2003 | 0.051997024271438 | | 2002 | 2.337301874543 | | 2001 | 2.9745008391957 | | 2000 | 0.73198198198161 | | 1999 | 0.82725060827251 | | 1998 | 1.1567807039134 | | 1997 | 1.7531647809724 | | 1996 | 2.7543066348241 | | 1995 | 7.8640078457011 | | 1994 | 32.293666856955 | | 1993 | 0.58643461512018 | | 1992 | 0.10994296708565 | | 1991 | -1.7535569019931 | | 1990 | 0.32509863018326 | | 1989 | 0.44730934077132 | | 1988 | -1.826682250793 | | 1987 | -4.1407237863381 | | 1986 | 6.1847785445693 | | 1985 | 13.000057615979 | | 1984 | 11.784027479633 | | 1983 | 11.616984568147 | | 1982 | 17.376385216892 | | 1981 | 5.9131937203163 | | 1980 | 8.7290276607233 | | 1979 | 9.6533598525703 | | 1978 | 3.4196510558752 | | 1977 | 11.340585637104 | | 1976 | 1.0830921871066 | | 1975 | 31.653423315368 | | 1974 | 16.601091509349 | | 1973 | 11.285310734684 | | 1972 | 6.1548841741127 | | 1971 | 3.8782026319754 | | 1970 | 2.8102481985703 | | 1969 | 4.0226534522571 | | 1968 | 0.058333332833043 |
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