What do you do when 20% of the population causes 80% of its problems? Possibly nothing.


Avshalom Caspi and colleagues have used the 45-year ‘Dunedin’ study in New Zealand to identify the ‘large economic burden’ associated with ‘a small segment of the population’. They don’t quite achieve the 20%-causes-80% mark, but suggest that 22% of the population account disproportionately for the problems that most policymakers would like to solve, including unhealthy, economically inactive, and criminal behaviour. Most importantly, they discuss some success in predicting such outcomes from a 45-minute diagnostic test of 3 year olds.

Of course, any such publication will prompt major debates about how we report, interpret, and deal with such information, and these debates tend to get away from the original authors as soon as they publish and others report (follow the tweet thread):

This is true even though the authors have gone to unusual lengths to show the many ways in which you could interpret their figures. Theirs is a politically aware report, using some of the language of elected politicians but challenging simple responses. You can see this in their discussion which has a lengthy list of points about the study’s limitations.

The ambiguity dilemma: more evidence does not produce more agreement

‘The most costly adults in our cohort started the race of life from a starting block somewhere behind the rest, and while carrying a heavy handicap in brain health’.

The first limitation is that evidence does not help us adjudicate between competing attempts to define the problem. For some, it reinforces the idea of an ‘underclass’ or small collection of problem/ troubled families that should be blamed for society’s ills (it’s the fault of families and individuals). For others, it reinforces the idea that socio-economic inequalities harm the life chances of people as soon as they are born (it is out of the control of individuals).

The intervention dilemma: we know more about the problem than its solution

The second limitation is that this study tells us a lot about a problem but not its solution. Perhaps there is some common ground on the need to act, and to invest in similar interventions, but:

  1. The evidence on the effectiveness of solutions is not as strong or systematic as this new evidence on the problem.
  2. There are major dilemmas involved in ‘scaling up’ such solutions and transferring them from one area to another.
  3. The overall ‘tone’ of debate still matters to policy delivery, to determine for example if any intervention should be punitive and compulsory (you will cause the problem, so you have to engage with the solution) or supportive and voluntary (you face disadvantages, so we’ll try to help you if you let us).

The moral dilemma: we may only pay attention to the problem if there is a feasible solution

Prevention and early intervention policy agendas often seem to fail because the issues they raise seem too difficult to solve. Governments make the commitment to ‘prevention’ in the abstract but ‘do not know what it means or appreciate scale of their task’.

A classic policymaker heuristic described by Kingdon is that policymakers only pay attention to problems they think they can solve. So, they might initially show enthusiasm, only to lose interest when problems seem intractable or there is high opposition to specific solutions.

This may be true of most policies, but prevention and early intervention also seem to magnify the big moral question that can stop policy in its tracks: to what extent is it appropriate to intervene in people’s lives to change their behaviour?

Some may vocally oppose interventions based on their concern about the controlling nature of the state, particularly when it intervenes to prevent (say, criminal) behaviour that will not necessarily occur. It may be easier to make the case for intervening to help children, but difficult to look like you are not second guessing their parents.

Others may quietly oppose interventions based on an unresolved economic question: does it really save money to intervene early? Put bluntly, a key ‘economic burden’ relates to population longevity; the ‘20%’ may cause economic problems in their working years but die far earlier than the 80%. Put less bluntly by the authors:

This is an important question because the health-care burden of developed societies concentrates in older age groups. To the extent that factors such as smoking, excess weight and health problems during midlife foretell health-care burden and social dependency, findings here should extend to later life (keeping in mind that midlife smoking, weight problems and health problems also forecast premature mortality)’.

So, policymakers find initially that ‘early intervention’ a valence issue only in the abstract – who wouldn’t want to intervene as early as possible in a child’s life to protect them or improve their life chances? – but not when they try to deliver concrete policies.

The evidence-based policymaking dilemma

Overall, we are left with the sense that even the best available evidence of a problem may not help us solve it. Choosing to do nothing may be just as ‘evidence based’ as choosing a solution with minimal effects. Choosing to do something requires us to use far more limited evidence of solution effectiveness and to act in the face of high uncertainty. Add into the mix that prevention policy does not seem to be particularly popular and you might wonder why any policymaker would want to do anything with the best evidence of a profound societal problem.


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Filed under Evidence Based Policymaking (EBPM), Prevention policy, Public health, public policy

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