This is the number of mail messages I actually saved per month; so it exclude spam and cron junk, and also excludes news postings. It does include LJ comments, starting from mid 2002.
find ~/Library/Mail -name '*.emlx' -print0 | xargs -0 grep -h -m 1 ^Date: | perl -ne 'use Date::Parse; s/Date: //; @d = strptime($_); $y=$d[5]+1900; printf "%d %02d\n",$y,$d[4] if 1990<$y and $y<=2008;' | sort | uniq -c > messages-per-month gnuplot <<'END' set term aqua set size 0.8,0.4 plot 'messages-per-month' using ($2+($3-1)/12):1 title "Messages per month" with line END
If you don't use Apple Mail you'll need to change the find and grep commands, and if you have a different way of getting pictures out of gnuplot you'll need to specify a suitable output terminal.
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