MW1e: Personnel

MechWarriors see an average of 250 combat encounters (almost half are artillery bombardments, aerospace strafing runs, infantry or minefields)* annually. A career lasts 26 years on average, and about 1600 end (retirement, dispossession or death) each year.

There's 5/6ths as many technicians as active MechWarriors, and their military careers last about 11 years on average.

There's 1/6th as many scouts as active MechWarriors, and they last about 14 months.

Sphere-wide...
About 80 regiments are deployed as full regiments.
About 350 battalions are deployed as separate battalions.
About 600 companies (350 full strength, the rest 9-11 Mechs) deploy independently.
More than 1800 other groups of 8 or fewer 'Mechs are deployed independently.

That's almost 2900 deployments, about 2000 of which are defensive (25/36, using my trick with the events table). The Inner Sphere only has 1700 settled star systems! Too few for a single deployment per system, and too many for a single deployment per world (assuming better than 1.2 inhabited worlds per system). Best explanation, I think, is that relatively few worlds have 'Mechs in permanent garrison, and that each garrison consists of one large group plus multiple small groups, scattered across the world.

How did I determine all that?

The event table has an entry for "new personnel," which should reflect how fast the authors meant MechWarriors, Techs, and Scouts to be replaced. To determine an overall rate I need to estimate the average number of MechWarriors in a party. This depends on how many player character MechWarriors the players started with. (This table will also tell me how frequently each unit size appears.)

I figure that one group of 2 needs to hook up with one group of 10 to form a full company; so if 10/36 groups of 2 make it to company size, and 21/36 groups of 10 make it to company size, then there must be 2.1x as many groups of 2 as there are groups of 10; figure groups of 4 hook up with groups of 8; and sometimes a group of 2 will hook up with another group of 2 to form a lance, or with a group of 6 to form 2 lances. From these various relationships it's possible to establish ratios between groups of 2, 4, 6, 8, and 10.

• Odd numbers (as calculated from the "Unit Size" chart) can't be fitted to the same curve, so I figure they're filler and am throwing them out.
• If you instead suppose (line in green) that the odd numbers ought to fall on the even numbers' (blue) curve, the odd values turn out basically symmetrical with the evens. (This is encouraging.)
• 8's can be calculated from 4+4 vs. 8+0 or from 4+8 vs 8+4; they yield different values, but if you bump the odds of 8 scoring a full company to 7-12, they become almost identical. I wonder if rows 8 and 9 originally scored a full company on rolls 7-12, and were changed to give the "PCs only" column a smoother progression. 

*My comment about artillery, strafing, infantry & mines comes from analysis of the Battlefield Events table, which I'll eventually get around to posting.