Opinion poll lessons reveal deficit in Government safety spending

The government currently uses the flawed VPF to determine spending on safety acr

The government currently uses the flawed VPF to determine spending on safety across several major departments, including the Department for Transport.

The government currently uses a measure known as the value of a prevented fatality or VPF to determine spending on safety across several major departments, including the Department for Transport.

In contrast with political opinion polls, which generally survey a minimum of 1,000 people to achieve the standard three per cent margin of error, the VPF is based on a survey of only 167 people, carried out 20 years ago. The research behind the new briefing shows that determining an accurate figure for the VPF by survey would require interviewing between 2,000 and 3,000 UK citizens.

Philip Thomas, professor of risk management in the Safety Systems Research Centre at the University of Bristol who authored the new research, said:

"The sample size was tiny compared with what it needed to be. The fact that so few people were questioned adds to the many problems surrounding the VPF. The methods used to interpret that 20-year-old survey have already been shown to be highly flawed. No confidence should be placed in the VPF that the Government uses to assess how much ought to be spent on safety."

Previous research by Professor Thomas has shown that using a survey to put a value on human life constitutes poor practice, which the USA discontinued some years ago in favour of "revealed preference" procedures. These can deduce people’s valuations from their actions. The Judgementor J-value method is a generalised, revealed preference technique developed at the University of Bristol, and this values human life about four times higher than the VPF, much more in line with US findings.

The Government’s support for the VPF means that it is used very widely in the UK as a yardstick to judge how much should be spent on health and safety measures, from road and rail transport, through reactor protection systems on nuclear power plant to the National Health Service, where it is used to estimate how much an extra year of healthy life is worth. According to Professor Thomas, the new results call the Government’s continued endorsement of the figure into question.

Lessons from political opinion polls: using surveys to value non-market goods such as human life , Policy Briefing, Philip Thomas: University of Bristol, December


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