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<font size=3><br><br>
</font><font face="Times New Roman, Times" size=4>May 24, 2006<br><br>
</font><h1><font size=5><b>The Politics of Paranoia and
Intimidation<br><br>
<br>
</i></font><font face="Times New Roman, Times" size=5 color="#990000">Why
Does the NSA Engage in Mass Surveillance of Americans When It's
Statistically Impossible for Such Spying to Detect
Terrorists?</b></font></h1><font face="Times New Roman, Times" size=5>By
FLOYD RUDMIN<br><br>
</font><font face="Verdana" size=6 color="#990000">T</font>
<font face="Verdana" size=2>he Bush administration and the National
Security Agency (NSA) have been secretly monitoring the email messages
and phone calls of all Americans. They are doing this, they say, for our
own good. To find terrorists. Many people have criticized NSA's domestic
spying as unlawful invasion of privacy, as search without search warrant,
as abuse of power, as misuse of the NSA's resources, as unConstitutional,
as something the communists would do, something very unAmerican.<br><br>
In addition, however, mass surveillance of an entire population cannot
find terrorists. It is a probabilistic impossibility. It cannot
work.<br><br>
What is the probability that people are terrorists given that NSA's mass
surveillance identifies them as terrorists? If the probability is zero
(p=0.00), then they certainly are not terrorists, and NSA was wasting
resources and damaging the lives of innocent citizens. If the probability
is one (p=1.00), then they definitely are terrorists, and NSA has saved
the day. If the probability is fifty-fifty (p=0.50), that is the same as
guessing the flip of a coin. The conditional probability that people are
terrorists given that the NSA surveillance system says they are, that had
better be very near to one (p_1.00) and very far from zero
(p=0.00).<br><br>
The mathematics of conditional probability were figured out by the
Scottish logician Thomas Bayes. If you Google "Bayes' Theorem",
you will get more than a million hits. Bayes' Theorem is taught in all
elementary statistics classes. Everyone at NSA certainly knows Bayes'
Theorem.<br><br>
To know if mass surveillance will work, Bayes' theorem requires three
estimations:<br><br>
</font>
<dl>
<dd>1) The base-rate for terrorists, i.e. what proportion of the
population are terrorists.<br><br>
<dd>2) The accuracy rate, i.e., the probability that real terrorists will
be identified by NSA;<br><br>
<dd>3) The misidentification rate, i.e., the probability that innocent
citizens will be misidentified by NSA as terrorists.<br><br>
</dl>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.<br><br>
I will not put Bayes' computational formula here. It is available in all
elementary statistics books and is on the web should any readers be
interested. But I will compute some conditional probabilities that people
are terrorists given that NSA's system of mass surveillance identifies
them to be terrorists.<br><br>
The US Census shows that there are about 300 million people living in the
USA.<br><br>
Suppose that there are 1,000 terrorists there as well, which is probably
a high estimate. The base-rate would be 1 terrorist per 300,000 people.
In percentages, that is .00033% which is way less than 1%. Suppose that
NSA surveillance has an accuracy rate of .40, which means that 40% of
real terrorists in the USA will be identified by NSA's monitoring of
everyone's email and phone calls. This is probably a high estimate,
considering that terrorists are doing their best to avoid detection.
There is no evidence thus far that NSA has been so successful at finding
terrorists. And suppose NSA's misidentification rate is .0001, which
means that .01% of innocent people will be misidentified as terrorists,
at least until they are investigated, detained and interrogated. Note
that .01% of the US population is 30,000 people. With these suppositions,
then the probability that people are terrorists given that NSA's system
of surveillance identifies them as terrorists is only p=0.0132, which is
near zero, very far from one. Ergo, NSA's surveillance system is useless
for finding terrorists.<br><br>
Suppose that NSA's system is more accurate than .40, let's say, .70,
which means that 70% of terrorists in the USA will be found by mass
monitoring of phone calls and email messages. Then, by Bayes' Theorem,
the probability that a person is a terrorist if targeted by NSA is still
only p=0.0228, which is near zero, far from one, and useless.<br><br>
Suppose that NSA's system is really, really, really good, really, really
good, with an accuracy rate of .90, and a misidentification rate of
.00001, which means that only 3,000 innocent people are misidentified as
terrorists. With these suppositions, then the probability that people are
terrorists given that NSA's system of surveillance identifies them as
terrorists is only p=0.2308, which is far from one and well below
flipping a coin. NSA's domestic monitoring of everyone's email and phone
calls is useless for finding terrorists.<br><br>
NSA knows this. Bayes' Theorem is elementary common knowledge. So, why
does NSA spy on Americans knowing it's not possible to find terrorists
that way? Mass surveillance of the entire population is logically
sensible only if there is a higher base-rate. Higher base-rates arise
from two lines of thought, neither of them very nice:<br><br>
<dl>
<dd>1) McCarthy-type national paranoia;<br><br>
<dd>2) political espionage.<br><br>
</dl>The whole NSA domestic spying program will seem to work well, will
seem logical and possible, if you are paranoid. Instead of presuming
there are 1,000 terrorists in the USA, presume there are 1 million
terrorists. Americans have gone paranoid before, for example, during the
McCarthyism era of the 1950s. Imagining a million terrorists in America
puts the base-rate at .00333, and now the probability that a person is a
terrorist given that NSA's system identifies them is p=.99, which is near
certainty. But only if you are paranoid. If NSA's surveillance requires a
presumption of a million terrorists, and if in fact there are only 100 or
only 10, then a lot of innocent people are going to be misidentified and
confidently mislabeled as terrorists.<br><br>
The ratio of real terrorists to innocent people in the prison camps of
Guantanamo, Abu Ghraib, and Kandahar shows that the US is paranoid and is
not bothered by mistaken identifications of innocent people. The ratio of
real terrorists to innocent people on Bush's no-fly lists shows that the
Bush administration is not bothered by mistaken identifications of
innocent Americans.<br><br>
Also, mass surveillance of the entire population is logically plausible
if NSA's domestic spying is not looking for terrorists, but looking for
something else, something that is not so rare as terrorists. For example,
the May 19 Fox News opinion poll of 900 registered voters found that 30%
dislike the Bush administration so much they want him impeached. If NSA
were monitoring email and phone calls to identify pro-impeachment people,
and if the accuracy rate were .90 and the error rate were .01, then the
probability that people are pro-impeachment given that NSA surveillance
system identified them as such, would be p=.98, which is coming close to
certainty (p_1.00). Mass surveillance by NSA of all Americans' phone
calls and emails would be very effective for domestic political
intelligence.<br><br>
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.<br><br>
Floyd Rudmin</b> is Professor of Social & Community Psychology at the
University of Tromsų in Norway. He can be reached at
<a href="mailto:frudmin@psyk.uit.no">frudmin@psyk.uit.no<br><br>
</a><x-sigsep><p></x-sigsep>
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