Logic model

A logic model is a structured, usually visual, representation of a program's theory of change, showing the logical chain from inputs and resources, through activities, to outputs, the immediate products of an activity such as people trained, and further out, to outcomes, the actual changes in behavior or condition the program is meant to cause.

A typical logic model lays out columns for inputs, activities, outputs, and short-, medium-, and long-term outcomes, connected by arrows that represent the assumed causal chain; more thorough versions also state the underlying assumptions and external factors that could affect that chain. It differs from a cost-benefit analysis, which monetizes results after they occur, and from a full program evaluation or randomized controlled trial, which tests whether the assumed chain actually held in practice; the logic model is the planning document evaluators later check reality against.

Building one forces program designers to be explicit about what they expect to happen and why, before money is spent, and it gives evaluators a map of what to measure and where the chain is most likely to break down. It also underpins the performance measures used in performance budgeting. A common pitfall is treating the model as a one-time planning exercise rather than revisiting it once evidence shows that an assumed link in the chain does not actually hold.