| Year | Value | | 2021 | 30,520.070482572 | | 2020 | 31,293.415999187 | | 2019 | 32,283.770717092 | | 2018 | 31,788.516090156 | | 2017 | 31,134.541943136 | | 2016 | 31,470.252917531 | | 2015 | 28,006.306867406 | | 2014 | 30,542.977693877 | | 2013 | 32,389.626830307 | | 2012 | 38,500.584185547 | | 2011 | 38,054.342202935 | | 2010 | 34,955.316195278 | | 2009 | 31,604.2766246 | | 2008 | 31,016.566917338 | | 2007 | 28,372.357660045 | | 2006 | 28,494.955449886 | | 2005 | 29,916.37675492 | | 2004 | 30,235.081846415 | | 2003 | 27,744.272425243 | | 2002 | 25,619.918225027 | | 2001 | 26,963.27591635 | | 2000 | 30,664.410441199 | | 1999 | 28,509.35820436 | | 1998 | 25,348.864560789 | | 1997 | 28,128.501040039 | | 1996 | 31,065.901673895 | | 1995 | 34,830.748925501 | | 1994 | 31,293.521187715 | | 1993 | 28,050.305684965 | | 1992 | 24,932.559807315 | | 1991 | 23,156.46076304 | | 1990 | 20,510.036184486 | | 1989 | 20,145.074904845 | | 1988 | 20,502.599690627 | | 1987 | 16,977.224514504 | | 1986 | 14,023.725828232 | | 1985 | 9,518.3045555894 | | 1984 | 9,025.1997448206 | | 1983 | 8,564.0647582828 | | 1982 | 7,882.8148074468 | | 1981 | 8,531.6704654244 | | 1980 | 7,869.3656148719 | | 1979 | 7,612.6515405164 | | 1978 | 7,402.388027704 | | 1977 | 5,295.6492715121 | | 1976 | 4,339.4940953884 | | 1975 | 3,877.4824270215 | | 1974 | 3,583.7457274759 | | 1973 | 3,263.7910951344 | | 1972 | 2,425.5503297119 | | 1971 | 1,864.8893891954 | | 1970 | 1,692.6623224612 |
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