Just wondering about the food issues the big AIs seem to suffer, leading to the collapse of big empires and subsequent lack of challenge for the player...

We've all had food problems (haven't we?) - when conquering a couple of territories coupled with a sudden building splurge suddenly puts your food into the red. But that's not a problem, usually by this point you're making thousands a turn so it's an easy matter to exempt the biggest food eating provinces from tax (and thereby taking them out of the whole food supply equation). Just wondered if the AI was programmed to do this, and if there was any way of checking if they ever did do this? Might explain a lot?