This is a preview. Log in through your library . Abstract Three forms of discontinuity in social structure produce linked analogous problems about aggregates or wholes: discontinuity in units, ...

In the early 19th century most people lit their homes with lamps that burned whale oil. In mid-century a Canadian physician and geologist named Abraham Gesner developed kerosene, a cleaner-burning ...

This is a preview. Log in through your library . Abstract Natural experiments provide robust identifying assumptions for the estimation of policy effects. Yet their use for policy design is often ...