Sunday, February 25, 2007

Combating domestic terrorism

The Age editorializes that the system of placing air marshals on planes to combat terrorism is an expensive failure. In 4 years the scheme has cost the government $106 million – about $26 million per year. The actual ticket cost of travelling – the marshal’s fly business class – is absorbed by the airlines and is an additional component of social cost. The Age points out that the marshals during the past 4 years have apprehended only 1 person with a small knife on a flight between Sydney and Cairns.

The national secretary of the Liquor, Hospitality and Miscellaneous Workers Union, Jeff Lawrence, said ‘There's just no evidence it's had any benefit.’ This might be so but that does not mean the scheme is wasteful. If the objective is deterrence it will be difficult to assemble evidence of effectiveness? Virgin Blue are also unhappy about the measure.

Federal Justice Minister Chris Ellison defended the use of marshals saying that every day without an incident was a successful day for aviation security. ‘It's like saying that because you have an armed guard outside a bank, and the bank is not robbed, the guard is unnecessary’. But Ellison is not right either unless he has evidence he does not present. One cannot assume attacks have been deferred by the marshals.

Some rough empirics however suggest that the use of marshals is unlikely to be excessively costly so Senator Ellison is partly right. Suppose the marshals deter just 1 terrorist attack on a plane every 10 years, an attack would have led to the deaths of 50 people. Supposing the value of each life lost is $5 million (this is conservative) there is a total human cost of $250 million which, including property damage costs, would cover current costs of the marshal program.

Of course the key issue is whether the same level of enhanced security might be provided more cheaply. Reinforcing cockpit doors, arming pilots with handguns and providing more effective passenger screening procedures (including computer-based selective screening of high-risk ethnic/religious groups linked to terrorism) prior to boarding will also deter terrorists. So too will surveillance of suspect groups including suspect religious groups to inform on those linked to espousing terrorist rhetoric.

Australia should also monitor the immigration and refugee program to limit entry of those ethnic/religious groups who pose greatest terrorist threat. The humanitarian program should be redirected towards Asia where we can address humanitarian concerns at lower risk to ourselves.
Determining whether marshals are a waste involves assessing risks as well as the costs and benefits of these alternative measures and whether it is best to go for a narrow or broadly based defense measures.

A terrorist attack in Australia is almost an inevitable consequence of our role in fighting terrorism in Afghanistan and Iraq and of our efforts in East Timor. This attack might be directed at aircraft, our ports or our mass transit systems.

Effective ways of addressing terrorism need to be systematically analysed using economics and operations research (an excellent survey with references is here) not on the basis of glib editorials that ignore the real threats we do face.


Damien Eldridge said...


Assessing the effectiveness of air-marshalls in reducing terrorism is plagued with the same problem that afflicts assessments of the effectiveness of any public policy. Indeed, this problem plagues many empirical studies ion the social sciences. This problem is the unobservability of the counterfactual. In effect, the counterfactual itself needs to be constructed. This will often require the use of some theory. There is a very nice discussion of these issues in the following paper by Dr Philippa Dee:

Dee, P (2005), Quantitative modelling at the Productivity Commission, Consultancy paper prepared for the Productivity Commission, Productivity Commission, Melbourne, December.

This paper is available at the following website: .

hc said...

Thank's Damien. Dee's paper would argue that one should model the determininants of terroridsm to assess the effects of a particular policy. I agree though it might be hard to get much out of what will be a host of guessed at parameter values here.

She emphasises econometrics. The appropriate tool here is game theory - a determined terrorist will react to any counter-terrorism measure by trying something else.

FDB said...

"a determined terrorist will react to any counter-terrorism measure by trying something else."

This is the key point for my money Harry - the more or less complete absence of any domestic terror attacks is what shows the marshalls to be unnecessary. If bombs were going off all over the joint but no planes were hijacked, then you could say that the marshalls were worth the trouble.

Francis Xavier Holden said...

I'm inclined to FDB's hydraulic theory. Block pipe here and pressure makes water pop out wherever is weakest. If the marshals had "prevented" say 5 oz air plane bombing then they should have displced that to say 4 bombings of Sydney Harbour bridge from a ferry, Melbourne Underground or Flinders Street Station

All marshals could do as far as I can see is possibly stop an actual hijacking by one or two actors. If one wanted to blow up a plane, say like Lockerbie, then no marshal can stop that.

Even hijacking, if you sent in 5 players on a plane and used two as decoys to draw out and identify marshalls then neutralised the marshalls you could still hijack to your hearts content.

I've never been convinced of the "suicide bombers / hijackers as geniuses " theory either. Mostly I reckon they are less than bright and superior intellegence gathering excercises at all points will largely stop them.

The problem is as Damien says evaluating the effectiveness of policy is difficult. A bit liek wearing a brass bracelett to stop arthiritis. Does it work. " Too right - never had arthritis since I wore it" - "Was it bad before?" - "Nope never had any."

Or say performance pay for teachers.

hc said...

There are game theoretic models one can use to see what is going on here. I think, for example, of tax-auditing games between a taxpayer and the tax office. These determine optimal cheating and inspection schedules. Apart from the analytics however it is ghard to fill these exercises out with real data.

Francis Xavier Holden said...

harry - this will make a good footnote for you one day:

An episode of The Simpsons (Season 7, "Much Apu About Nothing").

Springfield had just spent millions of dollars creating a highly sophisticated "Bear Patrol" in response to the sighting of a single bear the week before.

Homer: Not a bear in sight. The "Bear Patrol" is working like a charm!

Lisa: That's specious reasoning, Dad.

Homer: [uncomprehendingly] Thanks, honey.

Lisa: By your logic, I could claim that this rock keeps tigers away.

Homer: Hmm. How does it work?

Lisa: It doesn't work. (pause) It's just a stupid rock!

Homer: Uh-huh.

Lisa: But I don't see any tigers around, do you?

Homer: (pause) Lisa, I want to buy your rock.

hc said...

I like it FXH and used it myself before. And it summarises precisely the difficulty of evaluating such schemes.

Uncle Milton said...

I doubt whether you can use game theory to this problem, at least not where Al Qaeda are concerned. Game theory presupposes that people make rational choices many periods ahead, and work backwards to decide what is the rational decision now.

Al Qaeda operatives say they love death. This is not rational.

A more promising way to evaluate the marshal program is to look at what has happened since 9/11 in countries that don't have such a program. As far as I am aware, there have been no AQ hijackings anywhere, including countries with no air marshalls.

AQ now does different things. Putting air marshalls on domestic flights is fighting the last war.

hc said...

Uncle Milton, Maybe but I'd hate to be in the position of being responsible for 50 (or so) civilian deaths.

The enemy here are irrational beings who, as you say, don't value their own lives. Their objective is to kill civilian innocents.

So they act to best achieve that latter objective and you should be able to deduce something from that.

robert merkel said...

In my view, air marshals became redundant immediately after 9/11 (well, in the middle of 9/11, given the hypothesised actions of the passengers of Flight 93).

Essentially, before the attacks, passengers in a hijacked plane were prepared to sit tight, wait for the plane to land, and by either negotiation or violent derring-do by the local commandos be released. Now, however, passengers will risk their own lives to attack hijackers, because they know they can't rely on the hijackers to want to land the plane.

Frankly, a couple of armed air marshals are probably less able to defeat hijackers than two dozen unarmed but motivated passengers.