Turns out the man page of vmstat in procps was changed on Oct 8 2002:
http://cvs.sourceforge.net/viewcvs.py/procps/procps/vmstat.8?r1=1.1&r2=1.2
in reaction to a debian bug report:
http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=157935
--
Markus Bertheau <twanger(at)bluetwanger(dot)de>