FD really need to comment on the exact working of PP decay. There are lots of people under the belief that they can exploit PP by buying what they need every week to hit rank 5 (which they think would end up in massive profits after 4 or 5 weeks). Obviously you cant.
This is down to FD being as unclear as possible in the wording of the manual. A lot of people have posted about this and even started threads on it, unfortunately moderators keep closing them before any Dev has replied to them, basically hiding this info from the community and leading people down the wrong path, who are just going to come back with avengeance next week when they realise they are 100M+ worse off.
They also need to sort out this hidden overhead value nonsense for powers, how can we make proper decisions on where to expand too when we do not know how overheads(a value based on number of systems controlled by a power and separate from upkeep) affect our efforts, we could well be expanding our powers into systems that look like they are providing a lot of value, only for their hidden overhead cost to be astronomical and actually negatively affect our power. We have no way of seeing this and no way of combatting this effect (we cant chose to not expand somewhere if we have enough merits, unless we could contact every player in our power and co-ordinate our efforts).