A costing critically depends on the details of the specification of the proposed policy, as well as our assumptions about how people affected by the policy would be likely to change their behaviour in response to the policy.

Learn about our approach to determining the behavioural assumptions we apply when estimating the cost of policy proposals. We are guided by three principles. Behavioural assumptions aim to be:

  1. consistent across similar policies
  2. backed by empirical evidence
  3. informed by expert advice.


Understanding behavioural assumptions used in policy costings

Explore how we determine the behavioural assumptions that underpin our costings.  

Behavioural assumptions glossary

See individual assumptions, their justification and examples of use in costings.