| Year | Value | | 2022 | 19,176 | | 2021 | 19,301 | | 2020 | 19,413 | | 2019 | 19,476 | | 2018 | 19,454 | | 2017 | 19,346 | | 2016 | 19,147 | | 2015 | 18,885 | | 2014 | 18,595 | | 2013 | 18,297 | | 2012 | 18,006 | | 2011 | 17,715 | | 2010 | 17,380 | | 2009 | 16,945 | | 2008 | 16,463 | | 2007 | 15,999 | | 2006 | 15,537 | | 2005 | 15,101 | | 2004 | 14,714 | | 2003 | 14,362 | | 2002 | 14,024 | | 2001 | 13,657 | | 2000 | 13,259 | | 1999 | 12,849 | | 1998 | 12,438 | | 1997 | 12,068 | | 1996 | 11,746 | | 1995 | 11,457 | | 1994 | 11,160 | | 1993 | 10,810 | | 1992 | 10,439 | | 1991 | 10,193 | | 1990 | 9,972 | | 1989 | 9,658 | | 1988 | 9,382 | | 1987 | 9,183 | | 1986 | 9,076 | | 1985 | 9,088 | | 1984 | 9,202 | | 1983 | 9,309 | | 1982 | 9,343 | | 1981 | 9,287 | | 1980 | 9,101 | | 1979 | 8,836 | | 1978 | 8,542 | | 1977 | 8,206 | | 1976 | 7,845 | | 1975 | 7,481 | | 1974 | 7,196 | | 1973 | 6,979 | | 1972 | 6,755 | | 1971 | 6,532 | | 1970 | 6,282 | | 1969 | 5,965 | | 1968 | 5,618 | | 1967 | 5,286 | | 1966 | 4,981 | | 1965 | 4,716 | | 1964 | 4,493 | | 1963 | 4,316 | | 1962 | 4,184 | | 1961 | 4,095 | | 1960 | 4,025 |
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