| Year | Value | | 2021 | 34,466.630380857 | | 2020 | 30,620.226154399 | | 2019 | 32,104.600624895 | | 2018 | 32,963.837979005 | | 2017 | 30,505.1457604 | | 2016 | 28,848.281847725 | | 2015 | 28,094.984361279 | | 2014 | 32,770.264673456 | | 2013 | 32,096.742776566 | | 2012 | 30,824.376640307 | | 2011 | 33,434.463724513 | | 2010 | 30,899.81372757 | | 2009 | 31,611.010327283 | | 2008 | 34,822.769469113 | | 2007 | 32,197.090481139 | | 2006 | 28,200.015049689 | | 2005 | 26,591.692750528 | | 2004 | 25,806.304845609 | | 2003 | 22,510.959087168 | | 2002 | 18,391.250205204 | | 2001 | 17,035.212626584 | | 2000 | 16,906.188680824 | | 1999 | 18,646.880672263 | | 1998 | 18,755.721947986 | | 1997 | 18,286.815615665 | | 1996 | 20,051.524704237 | | 1995 | 19,834.703306299 | | 1994 | 17,199.620898145 | | 1993 | 16,371.435396974 | | 1992 | 18,037.856725145 | | 1991 | 16,448.835371738 | | 1990 | 15,977.76287248 | | 1989 | 12,780.667122341 | | 1988 | 12,571.698553853 | | 1987 | 11,446.394879304 | | 1986 | 9,254.3311231628 | | 1985 | 6,557.3642074701 | | 1984 | 6,383.4178562291 | | 1983 | 6,659.323036855 | | 1982 | 6,831.8299104363 | | 1981 | 7,120.6685328315 | | 1980 | 8,323.5904404486 | | 1979 | 7,515.9829729708 | | 1978 | 6,240.4408551288 | | 1977 | 5,104.2734242198 | | 1976 | 4,516.1295079939 | | 1975 | 4,342.7090474719 | | 1974 | 3,786.246606084 | | 1973 | 3,391.9063995272 | | 1972 | 2,630.0120823076 | | 1971 | 2,193.1682748355 | | 1970 | 1,951.147545051 |
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