Mr President,

I am pleased to learn that I am being considered as your next Science Advisor. Unfortunately, as a mathematician, I do not feel sufficiently well qualified for that position. I do, however, feel there is a clear and demonstrated need for someone on your team to offer advice on interpreting quantitative data, particularly when it comes to risk assessment. I would like to suggest that you create such a position, and I would be pleased to be considered for it.

For well understood evolutionary reasons, we humans are notoriously poor at assessing risks in a modern society. A single dramatic incident or one frightening picture in a newspaper can create a totally unrealistic impression. Let me give you one example I know to be dear to your heart. The tragic criminal acts of September 11, 2001, have left none of us unchanged. We are, I am sure, all agreed that we should do all we can to prevent a repetition.

Strengthening cockpit doors so that no one can force an entrance, as you have done, will surely prevent any more planes being flown into buildings. (El Al has had such doors for many years, and no unauthorized person has ever gained access to the cockpit.)

Thus, the remaining risk is of a plane being blown up either by suicide terrorists on board, by a bomb smuggled into luggage, or by sabotage prior to take-off. In any such case, the likelihood of significant loss of life to people on the ground is extremely low. So low that we can ignore it. The pilot of a plane that has been damaged while in the air will almost certainly be able to direct the plane away from any urban areas, and the odds that any wreckage from a plane that explodes catastrophically in mid-air are overwhelmingly that it will not land on a populated region.

I know that what I say might sound cavalier or foolhardy or uncaring. The hard facts the numbers present often fly in the face of our emotional responses and our fears. But the fact is, we have limited resources, and we need to decide where best to deploy them. This is why you need someone to help you assess risk.

That leaves the threat to the plane and the people on board. Let me try to put that risk into some perspective. For a single individual faced with a choice of driving a car or flying, how do the dangers of the two kinds of transport compare in the post September 11 world? We know the answer, thanks to a calculation carried out recently at the University of Michigan Transportation Research Institute. In order for commercial air travel to be as risky (in terms of loss of life) as driving a car on a major road, there would have to be a September 11 style incident roughly once every month, throughout the year.

Let me stress that this figure is not based on comparing apples and oranges, as some previous airline safety studies have done. By being based on the lengths of journeys, those previous studies made airline travel appear safer than it really is. The figure I have given you is based on the computed risk to a single individual. It compares the risks we face, for the journey we are about to take, when any one of us decides whether to board a plane or step into our car. In other words, "How likely am I to die on this trip?"

The answer, as the figures show, is that it would take a September 11 attack once every month before air travel offers the same kind of risk as car travel.

In short, most of the current effort being put into increasing airline safety is a waste of valuable resources. In a world where fanatical individuals are willing to give their own lives to achieve their goals, we can never be 100% safe. What we should do, is direct our resources in the most efficient manner possible.

In that connection, if you have not already done so, I recommend you see the movie The Sum of All Fears, where terrorists smuggle an atomic bomb into the United States in a shipping crate and detonate it in downtown Baltimore. Leaving aside the details of the plot, the risk portrayed in that film is real, and one where we would be advised (and I would so advise you) to put the resources we are currently squandering on airline security.

That is why you need expert assistance when it comes to interpreting the masses of numerical data that surround us, and putting those numbers into simple forms that ordinary human beings, including Presidents, can appreciate.

Numerically yours,

Keith Devlin
Executive Director of Stanford University's Center for the Study of Language and Information
Author of The Math Gene and The Millennium Problems.