A preference ballot allows voters to rank candidates in order of choice. Instant runoff voting (IRV) is a system that uses preference ballots to determine the winner by eliminating candidates and redistributing votes. Some US cities that use IRV include San Francisco, Oakland, and Minneapolis. Different theoretical perspectives on deviance include some acts being considered deviant in every culture while others view deviance as relative to cultural norms. Functionalism views on deviance are most useful for understanding as it examines how deviance fulfills certain functions for society.