Les assureurs comptent généralement sur les procurations émoussés pour évaluer le risque - âge, le sexe et l'état matrimonial , par exemple . Mais en supposant que tous les jeunes , conducteurs célibataires sont téméraires , par exemple , et que d'âge moyen , marié , les femelles sont prudents est souvent inexacte.

DRIVERS buying insurance from Progressive, an American insurer, get a choice: they can either supply a few bits of information about themselves and receive a quote based on the behaviour of similar people, or they can install a small gadget in their car. The device monitors their driving and adjusts the rate they pay accordingly. Those who refrain from braking sharply and stay off the roads at night can earn a discount of as much as 30% on the generic premium. For those who drive relatively little, Metromile, an insurer based in San Francisco, simply charges by the mile.

Discovery, a South African health insurer that has expanded to Europe and Asia, has 3m policyholders who have opted for a similar scheme. They can earn discounts by showing that they are looking after themselves, for example by wearing a device that monitors their fitness or by joining a gym. Oscar, a health insurer in New York, gives all its policyholders a fitness tracker; whenever they hit a set goal (walking 10,000 steps in a day, say) they get a refund of a dollar.

Insurers typically rely on blunter proxies to assess risk—age, sex and marital status, for instance. But assuming that all young, single, male drivers are reckless, for example, and that middle-aged, married, female ones are cautious is often inaccurate. It also involves unfair cross-subsidies: prudent and responsible young men help to pay for lead-footed mums.

Read More