The myth of 'evidence-based policymaking' in a decentred state

I describe a policy theory story in which a decentred state results from choice and necessity. Governments often choose not to centralise policymaking but they would not succeed if they tried. Many policy scholars take this story for granted, but it is often ignored in other academic disciplines and wider political debate. Instead, commentators call for more centralisation to deliver more accountable, 'rational,' and 'evidence-based' policymaking. Such contradictory arguments, about the feasibility and value of government centralisation, raise an ever-present dilemma for governments to accept or challenge decentring. They also accentuate a modern dilemma about how to seek 'evidence-based policymaking' in a decentred state. I identify three ideal-type ways in which governments can address both dilemmas consistently. I then identify their ad hoc use by UK and Scottish governments. Although each government has a reputation for more or less centralist approaches, both face similar dilemmas and address them in similar ways. Their choices reflect their need to appear to be in control while dealing with the fact that they are not.