| Year | Value | | 2014 | 263.51742934978 | | 2013 | 220.27910318176 | | 2012 | 217.3505463286 | | 2011 | 195.17935466117 | | 2010 | 179.3423834007 | | 2009 | 153.81741405551 | | 2008 | 134.0704097624 | | 2007 | 123.24003436486 | | 2006 | 114.59478676798 | | 2005 | 102.97700007688 | | 2004 | 87.196144501423 | | 2003 | 86.274858431365 | | 2002 | 81.355608593271 | | 2001 | 69.320609414251 | | 2000 | 82.513355280872 | | 1999 | 80.088438233323 | | 1998 | 54.09693595594 | | 1997 | 55.57288488128 | | 1996 | 59.172941638633 | | 1995 | 58.43558702347 | | 1994 | 59.19757945326 | | 1993 | 57.302062770484 | | 1992 | 59.458057482764 | | 1991 | 58.917545780308 | | 1990 | 60.784549307222 | | 1989 | 51.885472207752 | | 1988 | 54.708609673333 | | 1987 | 61.392354882215 | | 1986 | 60.238988886057 | | 1985 | 54.05489600043 | | 1984 | 50.141300899095 | | 1983 | 37.205091599523 | | 1982 | 39.550697457519 | | 1981 | 38.61106795456 | | 1980 | 42.102520717499 | | 1979 | 47.267162894664 | | 1978 | 48.609004974975 | | 1977 | 47.111865385788 | | 1976 | 46.42397803442 | | 1975 | 46.082461081991 | | 1974 | 45.093175317787 | | 1973 | 39.375790272512 | | 1972 | 33.5067834649 | | 1971 | 31.965251971455 |
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