How campaigns measure changes in behaviour
Launch library · evergreen read

Measuring behaviour change is harder than measuring stated opinion, since what people say they will do and what they actually do can differ considerably in practice, which means behaviour is often best measured through direct observation rather than self report alone, wherever that direct observation is genuinely practical to carry out.
Where direct observation is not practical, campaigns sometimes use proxy measures, such as sign ups, purchases or attendance, that are more closely tied to actual behaviour than a stated intention, though even these proxies carry their own real limitations worth acknowledging honestly to an audience, rather than glossed over for the sake of a tidier story.
Being upfront about the limits of whatever measure is used, rather than presenting a proxy as though it were a perfect record of behaviour, keeps a campaign's claims about impact appropriately modest and, over time, considerably more credible to sceptical observers and funders alike, who tend to notice overreach quickly.