I think this is a very good question, but numbers given by officials will be difficult to verify. It seems that the problem with foiling terrorist plots is not

I think this is a very good question, but numbers given by officials will be difficult to verify. It seems that the problem with foiling terrorist plots is not the amount of information that is available, but the inability to connect the dots: http://www.theguardian.com/world/2015/nov/16/french-and-belgian-intelligence-knew-paris-attackers-had-jihadi-backgrounds http://www.theguardian.com/world/2015/nov/16/french-and-belg... If anything, they should be asking (at least in Europe) for more personnel to keep better track of possible terrorists, because that is what has failed here. Another problem is that some countries have cut budgets of deradicalization programs and local eyes and ears since the mid-2000's. As we all know, the terrorist attacks are just a convenience for asking backdoors. Each opportunity is exploited.