| Year | Value | | 2022 | 19,403 | | 2021 | 20,031 | | 2020 | 20,557 | | 2019 | 20,931 | | 2018 | 21,146 | | 2017 | 21,217 | | 2016 | 21,199 | | 2015 | 21,124 | | 2014 | 20,974 | | 2013 | 20,733 | | 2012 | 20,393 | | 2011 | 19,965 | | 2010 | 19,312 | | 2009 | 18,498 | | 2008 | 17,750 | | 2007 | 17,091 | | 2006 | 16,522 | | 2005 | 16,031 | | 2004 | 15,621 | | 2003 | 15,298 | | 2002 | 15,045 | | 2001 | 14,860 | | 2000 | 14,738 | | 1999 | 14,671 | | 1998 | 14,667 | | 1997 | 14,739 | | 1996 | 14,871 | | 1995 | 15,035 | | 1994 | 15,199 | | 1993 | 15,298 | | 1992 | 15,289 | | 1991 | 15,042 | | 1990 | 14,504 | | 1989 | 13,847 | | 1988 | 13,183 | | 1987 | 12,512 | | 1986 | 11,824 | | 1985 | 11,115 | | 1984 | 10,384 | | 1983 | 9,652 | | 1982 | 8,943 | | 1981 | 8,264 | | 1980 | 7,624 | | 1979 | 7,047 | | 1978 | 6,549 | | 1977 | 6,141 | | 1976 | 5,825 | | 1975 | 5,581 | | 1974 | 5,376 | | 1973 | 5,186 | | 1972 | 5,006 | | 1971 | 4,791 | | 1970 | 4,530 | | 1969 | 4,282 | | 1968 | 4,082 | | 1967 | 3,922 | | 1966 | 3,783 | | 1965 | 3,655 | | 1964 | 3,531 | | 1963 | 3,407 | | 1962 | 3,290 | | 1961 | 3,181 | | 1960 | 3,059 |
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