[Kobal2]

2) Patrolling efficiency is based on the precision and action points of the units patrolling, the number of guys, and of course the patrol bonus if applicable. High precision and/or flying units are better at it, but they're also usually more expensive.

I find that, as a general rule, 10 average humans' worth of patrollers can reliably sort out the monthly unrest caused by a 10% tax hike. The real question is, of course : is it still worth it when it will cause the population to drop, and the patrollers' upkeep eats into the profits ?
Usually the answer is no, but a few nations can work with a high Growth, full on patrol & constant overtax strategy. Machaka, Bogarus, MA Tien Chi, Pangea and LA Man come to mind for example.