| Year | Value | | 2022 | 24,922 | | 2021 | 25,161 | | 2020 | 25,055 | | 2019 | 24,439 | | 2018 | 23,195 | | 2017 | 21,780 | | 2016 | 20,429 | | 2015 | 19,247 | | 2014 | 18,095 | | 2013 | 17,095 | | 2012 | 16,451 | | 2011 | 16,043 | | 2010 | 15,716 | | 2009 | 15,550 | | 2008 | 15,459 | | 2007 | 15,321 | | 2006 | 15,350 | | 2005 | 15,518 | | 2004 | 15,541 | | 2003 | 15,400 | | 2002 | 15,089 | | 2001 | 14,678 | | 2000 | 14,216 | | 1999 | 13,676 | | 1998 | 13,160 | | 1997 | 12,777 | | 1996 | 12,465 | | 1995 | 12,188 | | 1994 | 12,131 | | 1993 | 12,286 | | 1992 | 12,600 | | 1991 | 12,996 | | 1990 | 13,326 | | 1989 | 13,868 | | 1988 | 14,218 | | 1987 | 14,502 | | 1986 | 14,690 | | 1985 | 14,529 | | 1984 | 14,212 | | 1983 | 14,134 | | 1982 | 13,754 | | 1981 | 13,229 | | 1980 | 12,986 | | 1979 | 12,886 | | 1978 | 12,907 | | 1977 | 12,958 | | 1976 | 13,097 | | 1975 | 13,110 | | 1974 | 12,841 | | 1973 | 12,466 | | 1972 | 11,907 | | 1971 | 11,118 | | 1970 | 10,213 | | 1969 | 9,369 | | 1968 | 8,670 | | 1967 | 8,191 | | 1966 | 8,042 | | 1965 | 8,178 | | 1964 | 8,458 | | 1963 | 8,741 | | 1962 | 8,960 | | 1961 | 9,069 | | 1960 | 9,094 |
|