4.3. Doing without information on risk and exposure - an example
The following study on the effect of seat belts can serve as an example that demonstrates that it is not always necessary to use exposure data and calculate risks to measure the effect of a safety measure. Yet, the example also shows that omission of exposure data may result in inexplicable outcomes or mistaken conclusions. In 1983 a law requiring the use of safety belts in cars came into force in Great Britain. Subsequently, Professors Harvey and Durbin from the London School of Economics were asked to evaluate the safety effect of this law. Their results are described in Harvey & Durbin (1986). The authors looked at a time series of fatal and seriously injured car drivers and passengers over a period of fifteen years starting in 1969 and continuing till December 1984, two years after the introduction of the law (Figure 4).