Why the NSA’s warrantless surveillance doesn’t work
It’s a statistical impossibility.
To know if mass surveillance will work, Bayes’ theorem requires three estimations:
1. The base-rate for terrorists, i.e. what proportion of the population are terrorists;
2. The accuracy rate, i.e., the probability that real terrorists will be identified by NSA;
3. The misidentification rate, i.e., the probability that innocent citizens will be misidentified by NSA as terrorists.No matter how sophisticated and super-duper are NSA’s methods for identifying terrorists, no matter how big and fast are NSA’s computers, NSA’s accuracy rate will never be 100% and their misidentification rate will never be 0%. That fact, plus the extremely low base-rate for terrorists, means it is logically impossible for mass surveillance to be an effective way to find terrorists.
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But finding a few terrorists by mass surveillance of the phone calls and email messages of 300 million Americans is mathematically impossible, and NSA certainly knows that.
It’s my favorite kind of government program – both illegal and futile. That this also happens to be the only kind of action the Bush administration ever takes makes it even more fun. Data mining isn’t useless… it’s just useless when applied to this particular goal.
The math people at the NSA are smart enough to know this basic formulation, which naturally begs the question of why we the operation is ongoing anyway. The answer, of course, is that it was never really about terrorists or fighting a war, but about expanding the Executive’s control over the country. This is what happens when authoritarians take over all branches of the government.
