| Year | Value | | 2014 | -78.410803923156 | | 2013 | -78.530420324573 | | 2012 | -81.131877164402 | | 2011 | -79.829843980434 | | 2010 | -87.324087763005 | | 2009 | -92.063782036884 | | 2008 | -86.600723994081 | | 2007 | -78.251999110999 | | 2006 | -83.66338834277 | | 2005 | -76.069920914862 | | 2004 | -81.464383556865 | | 2003 | -77.575385596982 | | 2002 | -51.082481964156 | | 2001 | -35.283854641817 | | 2000 | -42.588794947245 | | 1999 | -28.525388103195 | | 1998 | -25.189840820357 | | 1997 | -30.846437854414 | | 1996 | -25.994771368287 | | 1995 | -35.534433651801 | | 1994 | -37.263139275449 | | 1993 | -30.947767166432 | | 1992 | -35.563107579257 | | 1991 | -45.578141763593 | | 1990 | -49.497015540802 | | 1989 | -65.875074994826 | | 1988 | -73.437338140778 | | 1987 | -80.480831932311 | | 1986 | -81.161018258686 | | 1985 | -92.005598594453 | | 1984 | -86.485932705732 | | 1983 | -87.26498963684 | | 1982 | -95.079775160205 | | 1981 | -95.067891958486 | | 1980 | -119.12708703779 | | 1979 | -113.19324095022 | | 1978 | -132.91536286169 | | 1977 | -155.75621867248 | | 1976 | -149.20743885046 | | 1975 | -148.97371875744 | | 1974 | -106.35703190505 | | 1973 | -84.16638390595 | | 1972 | -72.326315013607 | | 1971 | -81.652195689947 |
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