Ah, I need to finish that wiki article
Don't think we've even published the link to it actually, which is just as well until it's done.
Anyway:
- Initially, NextRawEventWaveSize = 10,000.
- Every Game Minute, each city hub adds 1000 to AccumulatedEventWaveCounter.
- When AccumulatedEventWaveCounter > NextRawEventWaveSize:
-- An attack is sent (with point value = AccumulatedEventWaveCounter)
-- NextRawEventWaveSize = Min(NextRawEventWaveSize * 1.25, maximumAllowableThreshold)
--- maximumAllowableThreshold is number of city hubs * 60,000
A capitol (if you choose to build one) counts as an additional city hub for this purpose, and the very last phase of the progression (if you choose to pursue it that far) has some alternate rules.