1999
January-February  7.5 MB
March-April  7.9 MB
July-August  7.9 MB
September-October  7.0 MB
November-December 7.8 MB

1998
January  6.1 MB
May-June  7.0 MB
November-December 7.1 MB

1997
January  6.3 MB
June  5.6 MB

1996
January  5.6 MB
June  5.6 MB
September  6.2 MB
December  6.2 MB

1995
January  5.0 MB
June  5.4 MB
September  4.5 MB
December  5.5 MB

1994
January  5.7 MB
June  5.3 MB
September  5.7 MB
December  6.1 MB

1993
January  5.7 MB
June  6.9 MB
September  5.8 MB
December  5.8 MB

1992
January  6.5 MB
June  5.7 MB
September  5.5 MB
December  6.2 MB

1991
January  6.7 MB
June  6.4 MB
September  6.6 MB
December  6.1 MB

1990
January  5.7 MB
June  6.3 MB
September  5.7 MB
December  6.1 MB

1989
January  5.9 MB
June  6.7 MB
September  6.2 MB
December  6.0 MB

1988
January  6.1 MB
June  5.5 MB
September  5.6 MB
December  6.2 MB

1987
February  5.8 MB
May  6.4 MB
August  6.1 MB
November  5.2 MB

1986
February  10.5 MB
May  5.8 MB
August  6.3 MB
November  8.4 MB

1985
April  11.4 MB
June  11.0 MB
September  11.2 MB

1984
December  8.2 MB