| Year | Value | | 2022 | 21,539 | | 2021 | 21,191 | | 2020 | 20,568 | | 2019 | 19,708 | | 2018 | 18,768 | | 2017 | 17,828 | | 2016 | 17,015 | | 2015 | 16,420 | | 2014 | 16,080 | | 2013 | 16,039 | | 2012 | 16,235 | | 2011 | 16,457 | | 2010 | 16,565 | | 2009 | 16,569 | | 2008 | 16,435 | | 2007 | 16,177 | | 2006 | 15,999 | | 2005 | 16,045 | | 2004 | 16,301 | | 2003 | 16,759 | | 2002 | 17,385 | | 2001 | 18,029 | | 2000 | 18,588 | | 1999 | 19,068 | | 1998 | 19,500 | | 1997 | 19,870 | | 1996 | 20,193 | | 1995 | 20,535 | | 1994 | 20,907 | | 1993 | 21,284 | | 1992 | 21,630 | | 1991 | 21,718 | | 1990 | 21,432 | | 1989 | 20,855 | | 1988 | 20,014 | | 1987 | 19,024 | | 1986 | 18,124 | | 1985 | 17,512 | | 1984 | 17,202 | | 1983 | 17,226 | | 1982 | 17,423 | | 1981 | 17,472 | | 1980 | 17,203 | | 1979 | 16,609 | | 1978 | 15,682 | | 1977 | 14,512 | | 1976 | 13,396 | | 1975 | 12,541 | | 1974 | 11,945 | | 1973 | 11,589 | | 1972 | 11,419 | | 1971 | 11,204 | | 1970 | 10,880 | | 1969 | 10,479 | | 1968 | 9,932 | | 1967 | 9,264 | | 1966 | 8,638 | | 1965 | 8,185 | | 1964 | 7,906 | | 1963 | 7,788 | | 1962 | 7,802 | | 1961 | 7,817 | | 1960 | 7,733 |
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