| Year | Value | | 2022 | 537 | | 2021 | 540 | | 2020 | 529 | | 2019 | 515 | | 2018 | 506 | | 2017 | 496 | | 2016 | 478 | | 2015 | 469 | | 2014 | 472 | | 2013 | 471 | | 2012 | 458 | | 2011 | 444 | | 2010 | 438 | | 2009 | 425 | | 2008 | 416 | | 2007 | 407 | | 2006 | 399 | | 2005 | 394 | | 2004 | 391 | | 2003 | 387 | | 2002 | 380 | | 2001 | 368 | | 2000 | 356 | | 1999 | 348 | | 1998 | 344 | | 1997 | 345 | | 1996 | 341 | | 1995 | 331 | | 1994 | 322 | | 1993 | 313 | | 1992 | 302 | | 1991 | 291 | | 1990 | 280 | | 1989 | 270 | | 1988 | 268 | | 1987 | 273 | | 1986 | 273 | | 1985 | 260 | | 1984 | 244 | | 1983 | 231 | | 1982 | 220 | | 1981 | 212 | | 1980 | 206 | | 1979 | 203 | | 1978 | 205 | | 1977 | 206 | | 1976 | 199 | | 1975 | 185 | | 1974 | 175 | | 1973 | 167 | | 1972 | 163 | | 1971 | 157 | | 1970 | 152 | | 1969 | 147 | | 1968 | 141 | | 1967 | 137 | | 1966 | 133 | | 1965 | 132 | | 1964 | 132 | | 1963 | 132 | | 1962 | 132 | | 1961 | 133 | | 1960 | 133 |
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