| Year | Value | | 2022 | 18,492 | | 2021 | 18,702 | | 2020 | 18,948 | | 2019 | 19,141 | | 2018 | 19,156 | | 2017 | 19,027 | | 2016 | 18,732 | | 2015 | 18,331 | | 2014 | 17,829 | | 2013 | 17,061 | | 2012 | 16,208 | | 2011 | 15,433 | | 2010 | 14,238 | | 2009 | 12,785 | | 2008 | 11,795 | | 2007 | 11,125 | | 2006 | 10,874 | | 2005 | 11,418 | | 2004 | 12,365 | | 2003 | 13,253 | | 2002 | 13,937 | | 2001 | 14,340 | | 2000 | 14,440 | | 1999 | 14,348 | | 1998 | 14,069 | | 1997 | 13,702 | | 1996 | 13,421 | | 1995 | 13,275 | | 1994 | 13,217 | | 1993 | 13,163 | | 1992 | 12,960 | | 1991 | 12,454 | | 1990 | 11,683 | | 1989 | 10,781 | | 1988 | 9,882 | | 1987 | 9,073 | | 1986 | 8,379 | | 1985 | 7,754 | | 1984 | 7,140 | | 1983 | 6,535 | | 1982 | 6,032 | | 1981 | 5,816 | | 1980 | 6,020 | | 1979 | 6,529 | | 1978 | 7,107 | | 1977 | 7,596 | | 1976 | 7,893 | | 1975 | 7,990 | | 1974 | 7,969 | | 1973 | 7,932 | | 1972 | 7,932 | | 1971 | 7,935 | | 1970 | 7,818 | | 1969 | 7,573 | | 1968 | 7,297 | | 1967 | 7,047 | | 1966 | 6,867 | | 1965 | 6,792 | | 1964 | 6,803 | | 1963 | 6,843 | | 1962 | 6,862 | | 1961 | 6,804 | | 1960 | 6,596 |
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