Intended for healthcare professionals

Feature Essay

Defending evidence informed policy making from ideological attack

BMJ 2018; 362 doi: (Published 10 September 2018) Cite this as: BMJ 2018;362:k3827
  1. Chris Bonell, professor of public health sociology,
  2. Rebecca Meiksin, research fellow,
  3. Nicholas Mays, professor of health policy,
  4. Mark Petticrew, professor of public health evaluation,
  5. Martin McKee, professor of European public health
  1. Faculty of Public Health and Policy, London School of Hygiene and Tropical Medicine, London, UK
  1. Corresponding author: chris.bonell{at}

The world faces a new era of greater hostility to experts and evidence, argue Chris Bonell and colleagues. The antidote, they say, is to remind the public how evidence based policy making evolved—and of its advantages and limitations

We seem to be entering a more ideological era, in which evidence informed policy must be defended. By “policy” we mean decisions made by local or central government about economics, rights and laws, regulations, police or military forces, welfare, and other statutory services, many of which affect health.

The belief that policy should be informed by evidence—derived from rigorous evaluations to find out what works—is relatively new. Some examples of large scale studies to inform policy, in areas such as agriculture and education, exist from the early 20th century. They were, however, limited to relatively few countries.

The evidence based medicine proponent Archie Cochrane observed, “It appears in general that it is Catholicism, Communism, and underdevelopment that appear to be against randomised controlled trials.”1 In many countries, decisions were made on the basis of ideology—such as Marxism-Leninism or belief in the free market, or what was considered innate knowledge—exemplified by the statement that “the gentleman [sic] in Whitehall really does know better what is good for people than the people know themselves.”2

The birth of evidence informed policy

Policy evaluation and the concept of evidence informed policy were born out of the tensions between conservatism, liberalism, and socialism that played out between the 18th and 20th centuries. Conservatives argued that societies should stick with tradition as the basis of policy because it represented the tried and tested product of the collective intelligence of past generations. Liberals demanded policy innovations to promote individual rights. Socialists sought radical economic reorientations to achieve fairness.

In the mid-20th century, scholars like Karl Popper, Robert Merton, and Donald Campbell converged …

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