Quantum nonlocality for each pair in an ensemble

Abstract If violations of Bell's inequality turn up in measurements on an ensemble of particle pairs, do they imply that each pair behaves nonlocally, or only the ensemble as a whole? We show that each pair in the ensemble behaves nonlocally when the particles are spins coupled in a singlet state. For spins in a nonsinglet state, however, a model in which some of the pairs behave locally reproduces quantum predictions.