Evidence and context
An organisation may have reports for individual programs and still struggle to answer a portfolio question: what changed across this body of work, for whom, and under which conditions?
ICAI's sustainable cities review encountered this problem. Inconsistent and insufficient results data prevented a quantitative analysis across the portfolio. The reviewers still identified positive achievements. Their in-depth program sample was also explicitly not fully representative. ICAI, UK aid for sustainable cities
Consider an illustrative portfolio in which one program counts people attending a session, another counts repeat visits and a third reports households reached. Adding those numbers would produce an impressive total with no consistent meaning. The source links might all work while the comparison remained invalid.
A useful evidence layer should therefore retain definitions, units, time periods and relevant population boundaries. It should distinguish observations from estimates and record when the same event appears in several documents.
Narrative material needs similar care. A lesson about maintaining a service after a grant ends should remain connected to the institutions, resources and conditions that made maintenance possible.
The practical test is whether a portfolio reader can understand both the pattern and its limits without rebuilding the analysis from the beginning.
Implications for research and practice
Portfolio aggregation requires comparable definitions, populations and observation periods. Shared labels alone do not make indicators comparable.
Scope and limitations
This is a selective narrative brief based on the linked publications, not a systematic review or a new empirical study. Illustrative scenarios and practice implications are editorial analysis. Findings should be interpreted within the settings, methods and observation periods of their original sources.