| Year | Value | | 2022 | 21,625 | | 2021 | 21,612 | | 2020 | 21,633 | | 2019 | 21,671 | | 2018 | 21,718 | | 2017 | 21,731 | | 2016 | 21,598 | | 2015 | 21,307 | | 2014 | 20,893 | | 2013 | 20,388 | | 2012 | 19,872 | | 2011 | 19,418 | | 2010 | 19,080 | | 2009 | 18,923 | | 2008 | 18,957 | | 2007 | 19,136 | | 2006 | 19,398 | | 2005 | 19,603 | | 2004 | 19,649 | | 2003 | 19,555 | | 2002 | 19,426 | | 2001 | 19,385 | | 2000 | 19,480 | | 1999 | 19,658 | | 1998 | 19,834 | | 1997 | 19,941 | | 1996 | 19,916 | | 1995 | 19,673 | | 1994 | 19,104 | | 1993 | 18,322 | | 1992 | 17,412 | | 1991 | 16,385 | | 1990 | 15,385 | | 1989 | 14,439 | | 1988 | 13,554 | | 1987 | 12,805 | | 1986 | 12,160 | | 1985 | 11,552 | | 1984 | 11,008 | | 1983 | 10,546 | | 1982 | 10,166 | | 1981 | 9,873 | | 1980 | 9,677 | | 1979 | 9,629 | | 1978 | 9,692 | | 1977 | 9,775 | | 1976 | 9,854 | | 1975 | 9,902 | | 1974 | 9,919 | | 1973 | 9,920 | | 1972 | 9,929 | | 1971 | 9,974 | | 1970 | 10,044 | | 1969 | 10,088 | | 1968 | 10,058 | | 1967 | 9,929 | | 1966 | 9,667 | | 1965 | 9,293 | | 1964 | 8,924 | | 1963 | 8,633 | | 1962 | 8,364 | | 1961 | 8,086 | | 1960 | 7,818 |
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