1. training military units takes idle population.
2. idle population is taxable population.
3. tax income decreases when you train population into units, due to 1.
4. barracks have queue slots, gaining more queue slots per level of barracks.
5. it has become apparent that idle population will NOT regrow as long as units continue to be trained, as evidenced by training all idle population in barracks, and no regrowth of population so long as those units continue to train.

6. It is therefor apparent that for purposes of regrowing population, they count as idle population, but for purposes of taxation and actual population in the city, they do NOT count.

7. lame ****.