The usefulness of the U.S. decennial census depends critically on the accuracy with which individual people are counted in specific housing units, at precise geographic locations. The 2000 and other recent censuses have relied on a set of residence rules to craft instructions on the census questionnaire in order to guide respondents to identify their correct "usual residence." Determining the proper place to count such groups as college students, prisoners, and military personnel has always been complicated and controversial; major societal trends such as placement of children in shared custody arrangements and the prevalence of "snowbird" and "sunbird" populations who regularly move to favorable climates further make it difficult to specify ties to one household and one place. Once, Only Once, and in the Right Place reviews the evolution of current residence rules and the way residence concepts are presented to respondents. It proposes major changes to the basic approach of collecting residence information and suggests a program of research to improve the 2010 and future censuses.

The issue of fair representation will take center stage as U.S. congressional districts are reapportioned based on the 2000 Census. Using U.S. history as a guide, the authors develop a theory of fair representation that establishes various principles for translating state populations—or vote totals of parties—into a fair allocation of congressional seats. They conclude that the current apportionment formula cheats the larger states in favor of the smaller, contrary to the intentions of the founding fathers and compromising the Supreme Court's "one man, one vote" rulings. Balinski and Young interweave the theoretical development with a rich historical account of controversies over representation, and show how many of these principles grew out of political contests in the course of United States history. The result is a work that is at once history, politics, and popular science. The book—updated with data from the 1980 and 1990 Census counts—vividly demonstrates that apportionment deals with the very substance of political power.