Object memory trending lower in 1.1.22 vs 1.1.20?

I've been graphing the memory usage (total accounted and storage mem
size) of Squid over the past several months, and once I upgraded to
1.1.22, about a week ago, it appears that the total memory in use for
hot objects has fallen -- it used to hover around 30MB, but now it's
around 5-10. <http://proxy.comshare.com/monitor/squid/squidmem.html>,
with no change to my cache_mem parameter, which is set to 24MB. Some
of the changes in the graph are a result of my attempts to keep Squid
from blowing past the 128MB memory limit by lowering the cache_mem,
but 1.1.22 was installed right around a week ago. Looking at the
yearly graph, you can see the last change to cache_mem at the
beginning of June.

Is this a result of improvements in the hot cache memory management,
differences in user access habits, or something else? Any guesses
would be appreciated.

        -Mike Pelletier.

--
 "[It will] be very hard to increase browser share on the merits of
  [Internet Explorer] alone.  It will be more important to leverage
  the OS asset to make people use IE instead of Navigator."
			-- Christian Wildfeuer, a Microsoft Manager