| Year | Value | | 2022 | 18,942 | | 2021 | 19,268 | | 2020 | 19,488 | | 2019 | 19,695 | | 2018 | 19,971 | | 2017 | 20,172 | | 2016 | 20,306 | | 2015 | 20,473 | | 2014 | 20,655 | | 2013 | 20,690 | | 2012 | 20,573 | | 2011 | 20,286 | | 2010 | 19,852 | | 2009 | 19,247 | | 2008 | 18,359 | | 2007 | 17,418 | | 2006 | 16,451 | | 2005 | 15,058 | | 2004 | 13,582 | | 2003 | 12,562 | | 2002 | 11,861 | | 2001 | 11,670 | | 2000 | 12,217 | | 1999 | 13,216 | | 1998 | 14,242 | | 1997 | 15,153 | | 1996 | 15,743 | | 1995 | 15,926 | | 1994 | 15,738 | | 1993 | 15,327 | | 1992 | 14,872 | | 1991 | 14,616 | | 1990 | 14,588 | | 1989 | 14,633 | | 1988 | 14,632 | | 1987 | 14,476 | | 1986 | 14,077 | | 1985 | 13,437 | | 1984 | 12,636 | | 1983 | 11,757 | | 1982 | 10,843 | | 1981 | 9,878 | | 1980 | 8,831 | | 1979 | 7,813 | | 1978 | 6,980 | | 1977 | 6,403 | | 1976 | 6,122 | | 1975 | 6,117 | | 1974 | 6,285 | | 1973 | 6,507 | | 1972 | 6,723 | | 1971 | 6,978 | | 1970 | 7,403 | | 1969 | 7,956 | | 1968 | 8,478 | | 1967 | 8,890 | | 1966 | 9,099 | | 1965 | 9,056 | | 1964 | 8,792 | | 1963 | 8,409 | | 1962 | 8,017 | | 1961 | 7,709 | | 1960 | 7,504 |
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