| Year | Value | | 2020 | 16.761689624821 | | 2019 | 17.709202456947 | | 2018 | 13.923906344114 | | 2017 | -2.6824169128434 | | 2016 | -4.9678177234238 | | 2015 | -10.086840983376 | | 2014 | -4.790794728712 | | 2013 | -5.4815151441455 | | 2012 | -12.663607097456 | | 2011 | 0.25043455213103 | | 2010 | -1.4712164236792 | | 2009 | -6.6016942248014 | | 1994 | -5.2856709146074 | | 1993 | 0.15355228804598 | | 1992 | -11.585188310319 | | 1991 | -5.67271271284 | | 1990 | -1.2222767495746 | | 1989 | 0.90795456340631 | | 1988 | 3.0911578186751 | | 1987 | -1.9007518586264 | | 1986 | 2.1971833123009 | | 1985 | 4.1798309755391 | | 1984 | 5.6644169740307 | | 1983 | -7.749489889123 | | 1982 | -5.4717793899744 | | 1981 | 2.1810250083304 | | 1980 | -1.619719782156 | | 1979 | -1.2530928351122 | | 1978 | 3.0273808623665 | | 1977 | 6.9608650616629 |
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