Year | Value | 2004 | 30.421149628467 | 2003 | 30.458818752029 | 2002 | 22.940723795216 | 2001 | 28.348570411507 | 2000 | 32.479973088132 | 1999 | 18.878932985344 | 1998 | 18.408179383763 | 1997 | 14.832520333623 | 1996 | 26.208892373452 | 1995 | 35.148685757412 | 1994 | 28.065407736304 | 1993 | 25.475983904988 | 1992 | 20.739589200585 | 1991 | 21.122210799253 | 1990 | 17.122792549128 | 1989 | 10.993498311667 | 1988 | 18.326903525703 | 1987 | 13.549347254783 | 1986 | 15.425665992379 | 1985 | 12.344109646052 | 1984 | 17.883430727473 | 1983 | 14.293572760166 | 1982 | 11.788908058555 | 1981 | 11.448154316047 | 1980 | 19.248529840338 | 1979 | 28.425840172714 | 1978 | 26.838753199918 | 1977 | 30.000063013145 | 1976 | 20.612717899589 |
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