| Year | Value | | 2022 | 18,287 | | 2021 | 20,057 | | 2020 | 21,119 | | 2019 | 21,300 | | 2018 | 20,977 | | 2017 | 20,462 | | 2016 | 19,913 | | 2015 | 19,547 | | 2014 | 19,553 | | 2013 | 19,787 | | 2012 | 19,781 | | 2011 | 19,428 | | 2010 | 18,726 | | 2009 | 17,650 | | 2008 | 16,266 | | 2007 | 14,561 | | 2006 | 12,702 | | 2005 | 10,991 | | 2004 | 9,546 | | 2003 | 8,460 | | 2002 | 7,876 | | 2001 | 7,699 | | 2000 | 7,767 | | 1999 | 8,044 | | 1998 | 8,434 | | 1997 | 8,932 | | 1996 | 9,593 | | 1995 | 10,267 | | 1994 | 10,811 | | 1993 | 11,207 | | 1992 | 11,459 | | 1991 | 11,535 | | 1990 | 11,399 | | 1989 | 10,832 | | 1988 | 10,276 | | 1987 | 9,911 | | 1986 | 9,400 | | 1985 | 8,870 | | 1984 | 8,369 | | 1983 | 7,927 | | 1982 | 7,536 | | 1981 | 7,206 | | 1980 | 6,960 | | 1979 | 6,809 | | 1978 | 6,757 | | 1977 | 6,801 | | 1976 | 6,909 | | 1975 | 7,075 | | 1974 | 7,324 | | 1973 | 7,656 | | 1972 | 8,014 | | 1971 | 8,316 | | 1970 | 8,519 | | 1969 | 8,603 | | 1968 | 8,539 | | 1967 | 8,324 | | 1966 | 8,052 | | 1965 | 7,820 | | 1964 | 7,640 | | 1963 | 7,500 | | 1962 | 7,407 | | 1961 | 7,342 | | 1960 | 7,263 |
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