| Year | Value | | 2022 | 18,861 | | 2021 | 19,226 | | 2020 | 19,101 | | 2019 | 18,389 | | 2018 | 17,488 | | 2017 | 16,577 | | 2016 | 15,772 | | 2015 | 15,094 | | 2014 | 14,479 | | 2013 | 13,805 | | 2012 | 13,058 | | 2011 | 12,302 | | 2010 | 11,502 | | 2009 | 10,736 | | 2008 | 10,136 | | 2007 | 9,698 | | 2006 | 9,356 | | 2005 | 9,138 | | 2004 | 9,142 | | 2003 | 9,324 | | 2002 | 9,673 | | 2001 | 10,336 | | 2000 | 11,252 | | 1999 | 12,146 | | 1998 | 12,987 | | 1997 | 13,848 | | 1996 | 14,670 | | 1995 | 15,415 | | 1994 | 16,127 | | 1993 | 16,761 | | 1992 | 17,227 | | 1991 | 17,522 | | 1990 | 17,610 | | 1989 | 17,384 | | 1988 | 16,783 | | 1987 | 15,825 | | 1986 | 14,542 | | 1985 | 13,084 | | 1984 | 11,639 | | 1983 | 10,327 | | 1982 | 9,271 | | 1981 | 8,569 | | 1980 | 8,297 | | 1979 | 8,345 | | 1978 | 8,460 | | 1977 | 8,474 | | 1976 | 8,331 | | 1975 | 8,041 | | 1974 | 7,779 | | 1973 | 7,774 | | 1972 | 8,134 | | 1971 | 8,936 | | 1970 | 10,084 | | 1969 | 11,180 | | 1968 | 11,980 | | 1967 | 12,533 | | 1966 | 12,892 | | 1965 | 13,092 | | 1964 | 13,134 | | 1963 | 13,014 | | 1962 | 12,740 | | 1961 | 12,315 | | 1960 | 12,200 |
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