Developing logic models for promising models
Where models are currently used on a small scale, they can be caught in the ‘evidence trap’: the numbers using them only enable small-scale, largely qualitative evaluations, which typically conclude that they are promising but ‘more research is needed’.
Some small-scale models already have sufficient evidence of outcomes and cost-effectiveness or savings to justify ambitious scale-up programmes. For others, a logic modelling approach would enable cases to be made for incremental investment based on testing the model’s outcomes against those which it claims will be delivered.
We recommend using Nesta’s Theory of Change approach to identify the model’s inputs, activities, assumptions and intended short- and longer-term outcomes and impacts for its target group(s). To make incremental investment in the model feasible, it is necessary to identify tangible reductions in, or avoidance of, costs to the system, as well as the outcomes most valued by the individuals and families using the service.
Savings could come from:
- the model being lower cost than traditional alternatives (e.g. Shared Lives)
- people typically needing to use support for a shorter time (e.g. hospital discharge support or reablement)
- people being less likely to use another service, or use of that service being delayed
- people being less likely to re-enter the service or another service (failure demand).
To develop a theory of change, you need to identify:
- Inputs: The contributions of staff, volunteers, resources and of the people who need support themselves and their families.
- Costs: Overall and unit costs of those inputs. E.g. how much does the model cost per individual or family it works with?
- Changes: The changes which the model aims to support people to make: e.g. lonely older people become more connected to others and feel less lonely.
- Outcomes: The key short- or longer-term health and wellbeing outcomes associated with those changes. This does not have to be an exhaustive list: instead focus on one or more outcomes which are likely to be associated with greater cost-effectiveness or savings, alongside the outcomes most valued by people themselves.
- Savings: The expected impact on health and care spend associated with those outcomes which are expected to have a tangible impact on costs and spending. How much will be saved or what typical cost is avoided each time the outcome is achieved?
This will enable you to set targets for the initial phase of the programme, based on the new intervention achieving sufficient cost-reducing outcomes to balance its costs.
An investment plan will be needed which includes regular review of the level of investment so that decision-makers can respond to good and poor outcomes.
Poor outcomes should lead to the intervention being redesigned, reduced or discontinued.
Good outcomes should lead to increasing investment.
Unless transition funds or social investment has been identified, this will usually require consideration of which other parts of the system may need to see reduced investment.