The idea and fetishizing of evidence-based policy is something we’re interested in at Arbitrary Constant. Here we wonder how many countries there are and what this might mean for Personal Health Budgets; here we explore what some of the biases and heuristics of evidence-based policy might be.
A news article about a lorry speed limit change (from 40mph to 50mph on single-track roads), an evidence-based impact assessment and competing interests was therefore bound to pique our interest.
The Daily Telegraph reported at the end of October:
The Government [has] pressed ahead with plans to raise the speed limit for lorries despite being warned of a likely increase in road deaths because it benefits the haulage industry
The information is generated by the government’s own impact assessment, the topline details of which are as follows:
- There are between 60 and 80 fatal accidents involving HGVs on relevant roads, of which an estimated 18 per year take place at between 36mph and 44mph
- Vehicles that travel between 36-44mph will be influenced by the increased speed limit – driving at an average of between 2.5-3.9mph faster
- This increase would result in 2.6-3.5 more deaths per year
- The potential benefit of reduced accidents from less overtaking is not included because there isn’t “sufficient confidence” it would happen
- On the benefits side, hauliers will save time (worth £13.8m), reduce costs (£2.5m) and government will gain more fuel duty revenue (£2.1m).
Far from bringing certainty to the situation, the evidence base has put us in a precarious position, hasn’t it? We can see this in two main ways.
- An evidence base has been put together and a policy position derived from it. Whether the evidence base is robust I don’t know, but it clearly involves some assumptions, parameters and interpretations that could be used, if someone were so inclined, to question the conclusions drawn.
- The evidence base says the change in policy will be good for one group (hauliers and government) to the tune of around £18m. At the same time it also says the change in policy won’t be good for another group, i.e. the approx. 3 additional people who would die because of the speed limit increase.
Nevertheless, the relevant Minister has pressed ahead with the increase in the speed limit.
To me, this is a clear demonstration of how it matters to what end, i.e. policy, means, i.e. the evidence base, are put. It reaffirms not only that evidence-based policy isn’t rational, predictable or benefit-maximising, but that it also doesn’t happen in a vacuum.
Policy nearly always means politics, and – to adapt a phrase – politics eats the evidence-base for breakfast.