Make the Govern City ledger state that cities are out of food instead of # of tuns in the billions to reach the next city level.
Also, a pop up to state that the city can not grow anymore do to lack of food would be nice.
That window has a column showing city growth rate. If thats showing zero then your out of food. 
As the other guy said, what would be really useful would be to add the display of the production amount for each city.
If you click on a city listed in the window, it will display that city after you close the ledger window. Which is kinda odd.
