Monsters have levels too

In D&D there are rules for how many men should there be of each level in a large group of men. Delta’s has observed that the

number and levels for leaders of groups of men in the OD&D campaign (in several different places) is surprisingly close to a simple divide-by-2 at each level

This seems like quite good system for any game, so how about an easy method to work out for a group of men, how many there are at each level?

One week later in Tenkar's Tavern, Eric mentioned "creatures with levels" and Nate McD commented

I have always liked the idea of ditching fixed HD for monsters, and adjusting their HD as appropriate... if there are 10 HD humans, why can't there be 10 HD orcs, goblins, or kobolds?

It's an idea I've considered before, and it's simple enough to give creatures levels - in D&D you add one HD per level, and in Explore you just give +1 attack, +1 parry, +1 Incap. But I don't want to have a group of fifth level orcs, I want a group of orcs with a fifth level leader, and what level you has always seemed a bit arbitrary.

So how about combing the two?

Calculating Levels for a Group of Monsters or Men

Whenever you meet a group of men or monsters, calculate the number at each level as follows: half the total (rounded up) are level one. Take the remainder, half of these (rounded up) are level two, etc.

An Example
A group of 35 bandits:

35 = 18 + 17 = 18 + 9 + 8 = 18 + 9 + 4 + 4 = 18 + 9 + 4 + 2 + 2 = 18 + 9 + 4 + 2 + 1 + 1.

You'd actually calculate this by repeatedly striking out the remainder and replacing it with a sum, and as soon as you get to a power of 2 you know the rest of the sequence thus:

35 = 18 + 17

Then you cross out the 17 to get:

35 = 18 + 17 9 + 8

Then you cross out the 8 and write in the remainder to get:

35 = 18 + 17 9 + 8 4 + 2 + 1 + 1

So 35 orcs, 18 first, 9 second, 4 third, 2 fourth, 1 fifth, 1 sixth.

Second Example

A group of 97 orcs:

97 =  49 + 48 24 + 24 12 + 12 6 + 6 3 + 3 2 + 1

So 49 first, 24 second, 12 third, 6 fourth, 3 fifth, 2 sixth, 1 seventh.

Observations

You always ends up with only one individual of the highest level, a single leader.

A leader of level n always has a group smaller than 2ⁿ. (rather than this being the average number). For example, you have a fifth level leader for groups sized 16-31.

The total strength of the party ends up being about 50% stronger than if they were all first level, so you might need to reduce the number in the group by one third.

I tried a random system, but it was time consuming and you get a wide variation in the highest level (roll d6 for all people. 1-3 means first level, discard these dice. Roll again to see who is second level. Repeat).

I didn't feel a need to persevere looking for a better random system - you can just jiggle them around a bit to make them more varied.

This seems appropriate for humanoids, but what about other creatures? What about a pack of Wolves? Giant Rats? Giant Hornets? I'm going to try it out!