For example, if Saudi provided 30 bbl/day, Nigeria 10, Canada 15, Iraq 15, Mexico 10, Venezula 20, and terrorists reduced Saudi output by 50% (not that hard), that would equate to a 15% global decrease in oil production. I pulled these numbers out of you know where, so I think the real impact would be much greater than 20%, which is very significant.
Lastdingo my percentages were pure speculation as stated (using American slang, so my apologies for not making that clear) to illustrate a point. However, I think we still disagree, because I think terrorists can have impact on oil production and transportation world wide, whether intended as an economic attack or not. I believe the insurgent/criminal attacks in Nigeria have reduced output in that country by 20% (I need to check my facts, but it is significant), the impact of terrorist and criminal attacks on the Northern Iraq oil fields has been significant (probably around 50% or more), and if you look at other locations around the world where terrorists are, or could, disrupt our global energy supplies, then I think you agree the threat is fairly significant. Look at it as a thousand pin pricks rather than a silver bullet attack on one critical node. Then again, there are locations where a silver bullet attack would have a significant impact.