Every message has a number assigned sequentially. For example, to see message number 700000 (the most recent round number), copy the following URL into your browser:

http://www.mudcat.org/detail.cfm?messages__message_id=700000

You will also see the date the message was posted. To see the exact time the message was posted, there is one more step: click the subject heading. This reveals that message number 700000 was posted at 28-Apr-02 - 05:42 PM.

Checking at intervals of 20000 messages, I saw that message 680000 was posted at 31-Mar-02 - 06:33 AM, and so on. I went back as far as message 440000, at 13-Apr-01 - 04:45 PM. I then put all this information into a spreadsheet. Adding some formulas, you can calculate the average number of messages per day for each interval of 20000 messages.

Here are my results.

Message  Date        Time      (*)
  ------  ---------   --------  ---
  700000  28-Apr-02 - 05:42 PM  n/a
  680000  31-Mar-02 - 06:33 AM  703
  660000  28-Feb-02 - 12:53 PM  651
  640000  01-Feb-02 - 09:31 AM  737
  620000  02-Jan-02 - 03:14 PM  672
  600000  29-Nov-01 - 01:33 AM  579
  580000  25-Oct-01 - 09:36 PM  585
  560000  27-Sep-01 - 01:31 PM  706
  540000  01-Sep-01 - 11:41 PM  782
  520000  02-Aug-01 - 06:21 PM  662
  500000  06-Jul-01 - 02:38 PM  737
  480000  09-Jun-01 - 10:15 PM  750
  460000  10-May-01 - 06:15 PM  663
  440000  13-Apr-01 - 04:45 PM  739

(*) Average messages per day for the period beginning on that date.

I leave you to your own interpretation, but I'm impressed by how consistent the numbers have been over the past year. Subjective impressions can be deceiving.