Lately I've been trying to get a better handle on my economy by watching my spending a bit more but one thing is really throwing me off. Countless times I'll set up a building and raise spending untill it says "1 week" yet the next turn it's annoyingly at 90% or some such. I finally got tired and tried to track down what behavior caused it and I couldn't really nail anything definitive.

So I looked into the PlanetImprovements.xml and looked up the cost of the building I was trying to build (Banking Center). It's listed as 250 so I setup spending such that I had 250 shields under social. Much to my irritation after hitting the turn button it wasn't finished!

So I'm stumped. Is this a bug? Why is it saying "1 week" and then sometimes not finishing in a week. Also why isn't it building based on the costs in PlanetImprovements.xml?