|Gygax Module Encounter Areas 1|
In the table above, the column marked "Empty" counts any room lacking a monster, trap, or treasure; but they are almost never literally bare. Most often this will be a fully-stocked storage chamber, supply room, armory, or at least some arcane decoration which foreshadows what is yet to come. Perhaps the closest one gets to a truly empty area are the galleries under clearance in the dungeon of G1, with only a few giant tools present. Contrast this with Rob Kuntz's WG5 module (1972-1973 design), which really does have many totally unkeyed/blank rooms on the map, with no defined contents whatsoever.
Initially I intended "Monster" to be a creature with zero treasure, in contrast to the "Monster & Treasure" entry. But midway through the assessment, I realized there was a bit of a problem; a common Gygax trope was to have some boundary guards with very small amounts of treasure (say, 1d6 or 2d6 sp or gp, something like that), and then a leader's chamber with a more sizable haul (hundreds or thousands of gold pieces). So later on I tried to put the "pocket change" bearing monsters in the first monster column, and the "major haul" monsters in the second; but this was extremely subjective, and I'm not sure that I always got it right (in retrospect, ideally I'd have some cutoff threshold for each dungeon based on adventuring level; perhaps someone else can improve on that). Again, contrast to Kuntz's WG5; most of the monsters there really have zero treasure.
The "Treasure" column represents halfway significant treasure with no monster guarding it, but is still often hidden, trapped, and/or dangerous to procure in some way. In the "Trick/Trap" column I counted things like actual traps, secret exits, penned-in captives (with a mixed of helpful and hurtful figures), possible allies, random magical effects, teleporting areas, aquatic travel challenges, etc.
Looking at the individual modules: S1 is of course infamous for being almost entirely trick/trap based, and it clearly shows up as an outlier in that sense above. S4 is a bit of a hack-fest; the lower level in particular is almost comical for every room, one after the other, being uniformly a huge monster with an equally huge treasure (somewhere I think I read Gygax saying he wrote this in a single weekend, and frankly, I think it shows; which is not to say that it's bad or something that I could replicate). G1-3 are of course the giant strongholds, organized and run in a coherent fashion for that purpose. G1 gives the appearance of more "empty" rooms, by virtue of its always-in-session celebratory feast (leaving many barracks and bedchambers devoid of occupants). D1-3 here only count the major encounter areas, not the minor encounters leading up the the main "dungeons" (arguably the out-areas function similar to a wilderness overland journey).
What I left for the end here: Module S3 deserves its own dissertation, as it is a wild, dense, and elaborately baroque one-of-a-kind adventure; it has the largest, most sprawling map of any of Gygax's modules, and any given area is liable to have a dozen crazy, new unique features just to liven up a particular room. At the same time, it is the only module in the list that reflects a particular old-school design sensibility: it has hundreds of rooms and areas which are actually unkeyed and blank on the map itself (although they are given a general guideline of having "jumbled furniture or rotting goods... inanimate skeletons..."). Meanwhile, levels II, V, and most of IV are enormous open areas, which made for a huge dilemma on my part about what to count as an "encounter area" (statistics above actually do count all of the separate empty rooms in S3; perhaps that was ill-advised).
Here's a design element that shows up in a few of these early modules that is not used later on: Re-using a particular key code for a very large number of small, similar monster lairs (S3 for its vegepygmy rooms and dangerous flora, S4 in the gnome lair, D1 for troglodyte caves, and D2 for Kuo-Toan pilgrim apartments). Which made a significant assessment coding problem: Should I count each of these minor rooms as a separate encounter area? Ultimately, I did count each one separately for S3, but did not count each separately for D1-2. (At least in D2, it would have added 45 rooms with monsters and 7 empty rooms.) I apologize for that discrepancy.
Now I wonder: Did anyone ever successfully run the S3 module? Just looking at the insane density of its maps and text (to say nothing of its special mechanics and illustration booklet, even a unique full-color insert!) leaves me trembling with fear at the prospect.