SuperFreakonomics: What is Variable X? (or how to catch a terrorist)

[ChiTownAbs, Inc]

Just finished reading SuperFreakanomics, which is a pretty explosive book. I actually thought the first book was better (maybe because it was so groundbreaking), and I've been following Dubner & Levitt on the NYTimes Freakanomics blog for the last couple of years as well.

Anyway, it's a quick read, and the last chapter is probably the best one.

One of the things I thought was interesting was a chapter on how to possibly catch a terrorist. Not to ruin too much of the book, the authors find that terrorists:

* Own a mobile phone
* Be a student
* Rent, rather than own, a home


These were neutral factors (they didn't seem to nail down a terrorist):

* Employment status
* Martial status
* Living in close proximity to a mosque


Contrary to preception, being single, unemployed, and living close to a mosque didn't mean you were a possible terrorist.

The authors continue and find that the terrorists were unlikely to:

* Have a savings account
* Withdraw money from an ATM on a Friday afternoon
* Buy life insurance


The ATM metric was a proxy for Muslim who attends that day's mandatory prayer service. Obviously, you're not going to buy life insurance if you know you're going to blow yourself up.

There is one more metric, which the authors call "Variable X". It's a behavioral metric, not a demographic one. It's a metric that produces a yes/no answer. Variable X measures the intensity of a particular banking activity. It's not unusual in low intensities among the general population, but occurs in high intensities much more frequently among those that have terrorist markers.

This marker allowed a bank to narrow down a customer base of 500,000 down to 30 potential terrorists.

Any clue what Variable X might be? (The authors claim that in the interest of national security, they've been requested not to disclose it)

[crazyronin]

Well, its really quite simple and after hours of thought, I've decided to tell al of you the one absolute way to tell if someone is a terrorist. Variable X is...Just a second, someone's knocking on the door.

[Nick Danger]

It's probably some form of money laundering. Frequent cash transactions just under the limit?

[Mrs. Danger]

I would think that someone who was planning to be a martyr (if that's who we are looking for) would only use a bank at all if it was necessary for his plans. This would be because he needs to buy something, and use a check (catalogue orders, and utility payments, for instance)

So, what I would look for is a checking account that only ever has the minimum in it. Deposits would be made, and immediately checks for the same amount would be cashed. The account would never have a high balance for any length of time, yet would never be overdrawn.

[redcat]

Originally Posted by ChiTownAbs, Inc

Just finished reading SuperFreakanomics, which is a pretty explosive book. I actually thought the first book was better (maybe because it was so groundbreaking), and I've been following Dubner & Levitt on the NYTimes Freakanomics blog for the last couple of years as well.

So is it worth $9.99 to get it for my Kindle? I hadn't really thought about it much until now, although I liked the first one.

Also, I have no idea what variable x is. Maybe it's some kind of geographical pattern they can trace as far as former places lived and time at each location.

[Decadance]

If you liked the first one, and consequently know anything about statistics, it is very likely the second book will just annoy you.

[Ranger]

Originally Posted by Nick Danger

It's probably some form of money laundering. Frequent cash transactions just under the limit?

I think that's a good guess.

And what about those frequent under limit transactions being international money transfers? Although I suppose that'd be demographical, not behavioral.

[Superboy]

I'd imagine it's a series of large deposits that are slowly withdrawn at a consistent rate until it is completely exhausted. There's no use having a bank account if you plan to disappear/blow yourself up.

[wendersfan]

Originally Posted by Decadance

If you liked the first one, and consequently know anything about statistics, it is very likely the second book will just annoy you.

I've not heard much good about the second one. I thought the first one was mildly interesting, but I'm annoyed at the trend by economists to study anything but economics, a trend of which the first book is emblematic. I know there's a great deal of overlap between many of the social sciences, but economists have gone nuts with some of this stuff.

[Shazam]

They wear turbans?

[Groucho]

Originally Posted by Shazam

They wear turbans?

That's an excellent way to catch a Sikh, but probably not relevant to the discussion.

[Mrs. Danger]

No thanks, I'm trying not to get Sikh.

[Decadance]

Originally Posted by wendersfan

I've not heard much good about the second one. I thought the first one was mildly interesting, but I'm annoyed at the trend by economists to study anything but economics, a trend of which the first book is emblematic. I know there's a great deal of overlap between many of the social sciences, but economists have gone nuts with some of this stuff.

You should see Andrew Gelman's multiple reviews of the book. They are, well, a bit rough.

[ChiTownAbs, Inc]

Originally Posted by redcat

So is it worth $9.99 to get it for my Kindle? I hadn't really thought about it much until now, although I liked the first one.

Also, I have no idea what variable x is. Maybe it's some kind of geographical pattern they can trace as far as former places lived and time at each location.

I just borrowed it from the library.

[wendersfan]

Originally Posted by Decadance

You should see Andrew Gelman's multiple reviews of the book. They are, well, a bit rough.

I've read 'em. I read Gelman's blog every day (his main one, not the new one he started).

[Decadance]

I would not be shocked to find that we probably read very similar blogs ><

[The Bus]

No, I don't think X is a terrorist.

[ChiTownAbs, Inc]

X may be a troll, but not a terrorist.

[arminius]

I thought he was the guy that replaced Christ?

[jadasion]

I think variable X is the way of life that person lives. Using the other variables mentioned to reduce it down, you could look for the one that does not stand out. For example, although the individual maybe an extremist, he won't be vocal. He will likely lead a lifestyle that does not get him in trouble. Rarely, if ever, deviating from a normal everyday routine.

[Renee]

Originally Posted by arminius

I thought he was the guy that replaced Christ?

[knobgoblin]

i believe variable x to be that the so called terrorist will most likely always make his withdrawals in the morning, and most likely many of these a week, possibly up to 7.

but thats just so i have closure.