one has to swim against the current.
Stanislav J. Lec[1]
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| In order to get to the source, one has to swim against the current. Stanislav J. Lec[1] |
And what do I do as the author of this book? It goes without saying that I would like you to read all of it, just as I wrote all of it. If you choose to read on, there is a chance, however slight, that you may afterwards feel that you could have put your time to better use. If, right now, you put it back on the shelf, you may later be nagged by the feeling that you missed out on an opportunity to learn something of importance to your own life expectancy, to that of your loved ones or to people in general. So, which of the two risky decisions do you take?
I chose a writing style and presentation of content that will, I hope, encourage you to read on. But, contrary to my intentions, you may judge my style too popular or too academic, the content too wide or too limited. By trying to reach large numbers of diverse readers, many a writer has in fact pleased very few, despite the vital importance of the topic to all.
So, both reader and writer engage in risk taking, although the possible consequences in this case may be relatively trivial. But there are more serious risks: those of accidents, injuries, substantial property damage, of death, disease and physical disability. It is these serious risks that form the main topic in the pages to follow.
A large number of these mishaps are the consequence of our daily actions, habits and lifestyles. We add to the probability of these mishaps every time we drive our car, board a plane, climb a ladder, have another cigarette or alcoholic beverage, cross the street, lift a heavy object, have sex with somebody we hardly know, light a fire, go swimming or jogging, handle work tools, and so on.
When mishaps occur, they usually involve comparatively few people, but as they are so common, these `minor' disasters add up to large numbers in a nation's statistics. Millions of people engage routinely, if not daily or even several times per day, in dangerous activities, and it is with their actions that this book is concerned. The focus will not be on the more infrequent decisions made by few people with potentially disastrous consequences for many, like deciding to go to war, to install and operate a nuclear plant, or to move dangerous cargo through a populous area.
In discussing statistics and research information on the more serious risks taken by large numbers of people, we will encounter many findings that may surprise at first. For instance, we all know that smoking cigarettes is associated with various diseases of heart and lungs, and thus with early death. And we know that stopping smoking reduces the likelihood of contracting these diseases. So you might expect a lower incidence of lung and heart disease amongst people who were told by their physician to quit smoking and who did quit. And your expectation would be right. These illnesses did, in fact, develop less often in this group.
However, if you also expected a lower mortality rate for this group, the facts prove you wrong. In one comparison between a group of quitters and a control group, the life-span of the quitters was found to be a little shorter![2] The difference in mortality rates between the quitters and the control group was not statistically significant, meaning that the probability of its occurrence on the basis of mere chance was greater than one in twenty. But, surely, these findings do not confirm common popular or common scientific expectation.
We all know that drivers who wear seatbelts are, on average, more likely to survive a crash than those who don't. So you might be inclined to expect that laws compelling drivers to buckle up, and that increase the seatbelt-wearing rate, will reduce a nation's traffic fatality rate per head of population.
You would probably expect similarly beneficial results from the construction of more crashworthy cars and the building of more forgiving highways. But again, this is not what has been found in fact.[3,4] To err is human. Our perceptions and reasonings are susceptible to mistakes. When looking at Figure 1.1, you will probably judge the line between the first and the second arrow (line a) to be longer than between the second and the third (line b). Measuring the two lengths with a ruler will soon convince you that your perception was wrong. If your ruler is precise enough, you will discover that line b is actually a little longer, by almost 1%.
Figure 1.1: Which line is longer, a or b?
All human beings are mortal.
Socrates is a human being.
Thus, Socrates is mortal.
The conclusion follows from the first two statements. Now consider the two arguments below:
In many accidents cars skid before they collide. Anti-lock brakes reduce the likelihood of skidding. Thus, installing such brakes will reduce the number of accidents.
Many intersection accidents involve cars colliding at right angles. Traffic lights reduce the frequency of right-angle collisions. Thus, installing lights will reduce the number of intersection accidents.
Because of the apparent similarity with the Socrates case, it may be tempting to assume that the conclusions in the two arguments are valid. The similarity, however, is deceptive and the conclusions are wrong. While Socrates himself--were he alive today--would be unlikely to fall victim to this trap, people often do. And people are more likely to agree with an erroneous conclusion when this fits their social attitudes and preconceptions. This is especially true for people who are not inclined to be analytical in the way they look at the world around them,[5] the 'fuzzy set' so to speak.
To err is human, but human, also, is awareness of that very fact. To the extent that this awareness helps to correct the error, further insight is gained and progress can be made. It has been said that popular wisdoms contradict each other, but then this observation itself is popular wisdom, too.
In some parts of the world, deaths due to floods in low-lying areas are a problem. The building of levees reduces the likelihood of floods. It might be expected that such constructions would reduce the number of flood victims. Once again, this is not what has been found in fact.[6] It may also come as a surprise that, in most developed countries, the mortality rates associated with violent death--mostly due to accidents--have remained virtually unchanged in the first three quarters of the current century, with the exception of war periods. These rates include fatal accidents of all types per head of population, and are corrected for historical variations in the gender and age composition of the populations concerned.[7] They show no clear downward trend, in spite of the massive technological, legislative, educational and medical advances made during the same period.
These observations seem difficult to believe. It also seems hard to comprehend why these rates are not much influenced by the visible progress in safety engineering, by prescriptive or prohibitive laws and their enforcement, by informing the public about risks, or by more successful medical treatment of accident victims who do not die instantly. What could possibly account for these and many other similar findings?
I suggest that all of the observations above may be explained by a relatively simple theory of human conduct in the face of risk, and that theory is the central theme of this book. The theory can be roughly outlined as follows:
Risk Homeostasis Theory maintains that, in any activity, people accept a certain level of subjectively estimated risk to their health, safety, and other things they value, in exchange for the benefits they hope to receive from that activity (transportation, work, eating, drinking, drug use, recreation, romance, sports or whatever).[8]
In any ongoing activity, people continuously check the amount of risk they feel they are exposed to. They compare this with the amount of risk they are willing to accept, and try to reduce any difference between the two to zero. Thus, if the level of subjectively experienced risk is lower than is acceptable, people tend to engage in actions that increase their exposure to risk. If, however, the level of subjectively experienced risk is higher than is acceptable, they make an attempt to exercise greater caution.
Consequently, they will choose their next action so that its subjectively expected amount of risk matches the level of risk accepted. During that next action, perceived and accepted risk are again compared and the subsequent adjustment action is chosen in order to minimize the difference, and so on.
Each particular adjustment action carries an objective probability of risk of accident or illness. Thus, the sum total of all adjustment actions across all members of the population over an extended period of time (one, or several years, perhaps) determines the temporal rate of accidents and of lifestyle-dependent disease in the population.
These rates, as well as more direct and frequent personal experiences of danger, in turn influence the amount of risk people expect to be associated with various activities, and with particular actions in these activities, over the next period of time. They will decide on their future actions accordingly, and these actions will produce the subsequent rate of human-made mishaps. Thus, a `closed loop' is formed between past and present, and between the present and the future. And, in the long run, the human-made mishap rate essentially depends on the amount of risk people are willing to accept.
In short, the theory of risk homeostasis proposes that a nation's temporal loss due to accidents and lifestyle-dependent disease is the output of a closed-loop regulating process in which the accepted level of risk operates as the unique controlling variable. Consequently, if we wish to make an attempt at reducing this misery, that attempt should be aimed at reducing the level of risk accepted by the population.
With this theory as a key, you now have the means to unravel the puzzling findings that have been mentioned so far. As you may have guessed, the key to understanding proposed in this book is the following notion:
People alter their behaviour in response to the implementation of health and safety measures, but the riskiness of the way they behave will not change, unless those measures are capable of motivating people to alter the amount of risk they are willing to incur.
We now have a plausible explanation for the fact that the technological efforts toward flood control in the USA failed to reduce the number of flood victims. Improved impoundment and levee construction did make certain areas less prone to flooding. But, as a consequence, more people settled in the fertile plains, because these now appeared `safe enough'. The end result was that subsequent floods, although fewer in number, caused more human loss and more property damage.6 If one wishes to reduce the problem of excessive flow of water, it would seem more sensible to seek a solution upstream--for instance in the form of reforestation or the careful maintenance of wetlands--so that more-than-normal precipitation is contained and does not run downhill.
We now have a possible explanation for the fact that a random selection of cigarette smokers who were advised to quit by their physician, did indeed reduce their cigarette consumption to a much greater extent than a comparison group. They did develop a lower frequency of smoking-related disease, but they did not live longer. In fact, their lives were a little shorter.
We now also have a possible explanation for the fact that the construction of modern multi-lane highways has contributed to a reduction in the number of road deaths per unit distance driven, while the number of traffic deaths per head of population remained the same or even increased. Consider the following argument:
A river empties into the sea through a delta.
The delta has three channels, all of equal size.
Therefore, damming two of the channels will reduce the
flow of water to the sea by two-thirds.
In all likelihood, you will not accept this argument. This isn't surprising, because it is so obviously wrong. One cannot stem the flow as long as there remain alternative routes to the destination. One cannot reduce mortality due to accidents and lifestyle-dependent disease unless all opportunity for premature death were eliminated by law or made impossible through technological intervention. And that, of course, can never be fully achieved. In the case above, the river would simply develop a fourth channel.
What is perhaps more surprising, then, is that safety and health authorities have traditionally told people what they should or should not do to avoid injury or lifestyle-dependent disease, without offering them motivation to reduce risk, without offering them a reason to live longer. And what may be more surprising still is that the wisdom and effectiveness of this prevention practice is so rarely questioned. The `delta illusion' is a very powerful illusion indeed.
It is obvious that a sure way to reduce the accident rate on a particular road to zero is to simply close that road to all traffic. It is almost as obvious that road users will move to other roads and that the accidents will migrate with them to other locations. Road closure is no effective remedy. Obvious, isn't it? So why should prohibiting drinking and driving, or closing the borders to the illicit drug trade, be effective remedies? To believe so is to fall victim to the delta fallacy.
The chapters following call the traditional prevention practice into question. Specifically, it is argued that the traditional reliance on enforcement of laws, on informing the public of certain dangers, and on engineering the physical features of the human-made environment is not very productive towards greater health and safety insofar as these are dependent on human conduct. An effort is made to explain why this is so.
At first, this may appear to be a pessimistic exercise, but nothing could be further from the truth. The theoretical ideas, developed for the purpose of explaining the limited success of the traditional approach, also point the way to the design of effective safety interventions. Not surprisingly, these alternative interventions are aimed at increasing people's desire to be safe and to live a healthy style of life. Thus, as an alternative to the enforcement, educational, and engineering approaches of the past, a motivational approach to prevention is presented. This is an approach that offers people a reason to live longer and, therefore, to adopt safer and healthier ways of life. The documented experience obtained with this strategy to date strengthens confidence that it is considerably more effective than the traditional approaches. And because the motivational approach seems to cause fewer negative side-effects than the traditional countermeasures and to be cheaper to implement, it also offers hope for a happier society throughout.
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