Intelligence war

[rockman]

To follow on in my game - (if anyone is still interested!) i have been using my intelligence to bLast the Sergetti, the main threat to my empire. I have been using the "food contamination" against them and I reckon I must have successfully contaiminated between 15-20 of their planets. The question I have is whether there are degrees of sucess eg small number of population die, sizable number die, all population dies etc. I always seem to get the message that "a sizable percentage of the populaton has died" what exatly does that mean?
I have had a few intel attacks slip through my counter intel (those bloody drakol!) and they have used food contamination against my planets. However in those cases ALL my population of the planet has died, not just a sizable percentage. Also my attacks do not seem to have significantly reduced the population or resources of the Sergetti empire much - I have checked it out on the Empire comparison graph.
Can anyone please shed some lght on this?

Thanks!