What changes behaviour at scale

The domain's own question is which levers change what people do at the scale of a population, and the evidence has become good enough to rank them. Price works, and works most for the heaviest users: minimum unit pricing in Scotland reduced alcohol-specific deaths by around a tenth against a control, tobacco taxes have the longest record of any health intervention, and sugar levies changed what was sold within a year. Availability works: smoke-free laws were followed by measurable falls in heart-attack admissions, and outlet density and opening hours move alcohol harm. Defaults work where there is a default to set: a fixed appointment rather than an open invitation raises screening attendance, and opt-out framing does the same for vaccination and organ donation. Reminders work modestly and cheaply — text messages lift vaccination by a percentage point or two, reliably — and incentives work in some settings and not others: paying pregnant women to quit smoking is effective in trials, while vaccine lotteries in the United States moved nothing. Information on its own does least: campaigns and labels change awareness more than behaviour. The pattern is that structural measures beat informational ones, and that informational measures can widen inequalities while price and defaults tend to narrow them.

The behaviours where this matters most for mortality are the ones this page takes as its own subject: uptake. Whether people take the vaccine, attend the screening, fill the prescription and keep filling it is the gap between what works in a trial and what happens in a population, and it is a behavioural gap. Childhood vaccine coverage has fallen in most high-income countries since 2020 and measles has returned where it fell furthest; seasonal vaccination of older people is high in some countries and falling in others; screening attendance is the steepest social gradient on the site, with a twenty-point difference between the most and least deprived in the English bowel programme; and around half of long-term medication for chronic disease is not taken as prescribed, which for cardiovascular drugs alone represents a share of deaths the new medicines cannot make up. Persistence with the GLP-1 drugs is the newest instance and may prove the largest.

What the evidence does not yet show is durability and transfer: whether effects measured over a year hold over a decade, and whether a lever that moved one behaviour in one country moves another elsewhere. The replications are rare, the trials short, and the null results underpublished.

Status

building

Direction

strengthening

Would change our view

A national series showing coverage, attendance or adherence responding to a specific intervention and staying there; a well-powered replication failing for a lever thought established, or succeeding for one thought weak; or evidence that a scaled nudge widened a mortality gap.

Trackers

Gaps

Long-run follow-up of almost any intervention; adherence measured outside claims data; uptake by social group outside the UK, the Nordic countries and the United States; interventions evaluated in Japan or Korea.