The game guide states that
Clear enough. But are there any modifiers that affect the above. I ask this because of a current debate we are having elsewhere about how effective SDI is. As an example, during my last war, I was hit repeatedley with Nuclear Missiles, and indeed my SDI only stopped one inbound nuke, however, others have reported far greater success with SDI. The nation I was fighting had approx 1000 more tech than I and presumably this has a bearing on it. Conversely, my opponents SDI stopped four of mine getting through.