HOW TERRORISTS EFFECT OUR N...

"Whoever was behind [the Marathon] attack killed a few, wounded scores, and scared millions. There's a term for this: asymmetrical warfare. An opponent with inferior resources, manpower, and technology can nevertheless inflict disproportionate damage on an enemy. The ultimate example of this concept, of course, was September 11, 2001, when 19 hijackers spending just $500,000 — well, you know what they did. But the true impact the 9/11 hijackers had went far beyond the physical damage they inflicted that day. September 11 caused us to burn through trillions on the two longest wars in our history, vastly expand our national security and intelligence bureaucracy, and give up a portion of our civil liberties. And yet for all that: Do you feel safer?  What more can we do?"

Here is a thought provoking article with important relevant data-

http://theweek.com/bullpen/column/242776/the-lessons-of-boston