Playing on larger maps there's a considerable issue with moving ships to be battle area when on the offensive. Hence in the end game it becomes meaningless to produce new ships which will never see action. At the same time your empire is approaching a stage where most social projects are already built or if not yet completed they will never have time to provide ROI.
On the basis of this I went for 0% spending in one game and put 500-1000 per turn into destabilisation for each enemy race. It seemed to me that their planets fell more quickly when invaded (ie lower morale) and also that their economies tanked (presumably as they reduced SOC/MIL/RES spending to increase propaganda instead). To my regret I wasn't actually taking notes though so I can't quantify the impact to alien economies.
Has anybody else experimented with this? Any thoughts on its efficiency or any drawbacks?
BTW, if this is considered cheese then I'd suggest an easy control would be to allow the espionage and destablisation sliders to be *target investment* with *actual investment* only increasing by 1 notch per turn. This wouldn't add any micromanagement but it would stop the instant ability to project or cancel massive espionage and agitprop programs across vast distances.
I have observed the same effect with destabilization. Although I also lack empirical evidence, the greatest effect of funding destabilization mid- to late-game is to force the target AI out of the higher forms of government and back into Republic or Imperium. Combined with the need to lower taxes, and for propaganda (plus any consequent loss due to trade route disruption), destabilization is a useful tool for forcing the enemy Empire into debt.
However, once the AI adjusts itself downward to Republic/Imperium and rebalances its income vs. expenditures, I find destabilization drops off dramatically in effectiveness.
Thus, I use an oscillation strategy. If I am declared war upon, I immediately boost destabilization to 100%. I have seen some target Empires go as much as -1500bc into debt, and completely stop producing, within 1-3 turns of this. I keep it there until the AI recovers (which I define as having a positive cash balance of >200bc's). Once recovered, I reduce destabilization to 10-20% (2-3 notches on the slider) and maintain espionage at the same rate (or slightly better, if I have the extra income). This delays (or sometimes prevents) the AI from re-establishing Democracy or Federation, and limits the effectiveness of its own efforts against me.
I believe this is the most effective way to use destabilization. However, long-term expenditures (a marginal rate applied each turn over time) is effective at promoting defections to the I-League, especially for newly conquered or settled AI planets. I use this strategy when I see a neighboring AI conquering minors, but do not want to openly declare war or ally with anyone against it.