| Year | Value | | 2022 | 24,897 | | 2021 | 24,763 | | 2020 | 24,739 | | 2019 | 25,130 | | 2018 | 25,189 | | 2017 | 25,017 | | 2016 | 25,356 | | 2015 | 25,607 | | 2014 | 25,734 | | 2013 | 25,737 | | 2012 | 25,689 | | 2011 | 25,757 | | 2010 | 25,938 | | 2009 | 26,132 | | 2008 | 26,343 | | 2007 | 26,539 | | 2006 | 26,690 | | 2005 | 26,770 | | 2004 | 26,770 | | 2003 | 26,706 | | 2002 | 26,634 | | 2001 | 26,560 | | 2000 | 26,457 | | 1999 | 26,312 | | 1998 | 26,110 | | 1997 | 25,837 | | 1996 | 25,475 | | 1995 | 25,021 | | 1994 | 24,496 | | 1993 | 23,931 | | 1992 | 23,376 | | 1991 | 22,799 | | 1990 | 22,350 | | 1989 | 22,035 | | 1988 | 21,625 | | 1987 | 21,097 | | 1986 | 20,461 | | 1985 | 19,751 | | 1984 | 19,019 | | 1983 | 18,329 | | 1982 | 17,736 | | 1981 | 17,260 | | 1980 | 16,926 | | 1979 | 16,691 | | 1978 | 16,496 | | 1977 | 16,334 | | 1976 | 16,205 | | 1975 | 16,112 | | 1974 | 16,058 | | 1973 | 16,033 | | 1972 | 16,011 | | 1971 | 15,973 | | 1970 | 15,947 | | 1969 | 15,922 | | 1968 | 15,853 | | 1967 | 15,758 | | 1966 | 15,645 | | 1965 | 15,517 | | 1964 | 15,383 | | 1963 | 15,237 | | 1962 | 15,058 | | 1961 | 14,828 | | 1960 | 14,559 |
|