Spruce wrote: ... it seems I lose the pop up screen after stopping my investments a few turns later?
I'm not sure what pop-up screen you are referring to. Investment improvements are displayed in the text message area for each turn. Each new factory gets its own line in the text field.
As long as you have a factory or three in a state and the next turns projected income is still in the black, then there is a chance improvements can occur in that states cities. The number of factories simply increases the odds each city in that state gets a positive die roll. The factory graphic in the ledger itself is not permanent, it's simply an indicator of that turns expenditures.
Improvements are not guaranteed, expenditures just allow you to get a random chance in your cities for an improvement that turn. But if you're in the red on projected income, chances are there won't be any industrialization die rolls even though you see factories on your ledger screen.
I read somewhere that the engine cancels the last item built and so on down the list of whatever you produced if projections are in the red, but I'm not sure about that.
Stay in the black and you'll continue to get rolls each turn. Improvements themselves are permanent. Mouse over each city, the improvements show up up top under your national production numbers and you'll see them increase as new factories get built.
Jim