| Year | Value | | 2018 | 36,072.663208372 | | 2017 | 34,065.891026246 | | 2016 | 34,104.356814245 | | 2015 | 37,441.028418364 | | 2014 | 39,539.116496386 | | 2013 | 36,085.945954118 | | 2012 | 35,519.330194016 | | 2011 | 35,752.958196581 | | 2010 | 33,571.199311961 | | 2009 | 32,299.433940171 | | 2008 | 39,510.517146628 | | 2007 | 42,710.970879922 | | 2006 | 37,973.615193148 | | 2005 | 36,605.041787585 | | 2004 | 35,034.761253561 | | 2003 | 29,959.883518765 | | 2002 | 26,117.410793852 | | 2001 | 24,062.701850481 | | 2000 | 24,401.020433157 | | 1999 | 24,834.767237857 | | 1998 | 24,813.523591514 | | 1997 | 22,819.647257645 | | 1996 | 20,267.474565192 | | 1995 | 19,281.295869874 | | 1994 | 17,726.879047973 | | 1993 | 16,162.179534613 | | 1992 | 17,960.752837891 | | 1991 | 17,154.961942899 | | 1990 | 16,398.081944205 | | 1989 | 14,122.77927203 | | 1988 | 14,080.336635695 | | 1987 | 11,526.690504636 | | 1986 | 9,409.8897386152 | | 1985 | 7,476.5892037075 | | 1984 | 7,145.8609084462 | | 1983 | 7,601.0905342777 | | 1982 | 7,969.2426627038 | | 1981 | 8,319.6777518481 | | 1980 | 8,807.363458651 | | 1979 | 6,967.8616617843 | | 1978 | 5,473.1969292658 | | 1977 | 4,308.6589511442 | | 1976 | 3,891.152906131 | | 1975 | 4,064.5549930623 | | 1974 | 3,456.5072802286 | | 1973 | 3,246.470747077 | | 1972 | 2,881.7077382368 | | 1971 | 2,534.2704865063 | | 1970 | 2,267.4500398324 |
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