To answer the first question, Teresa Sullivan examines yardsticks in use, demonstrates their inadequacy, and develops a different measure that is easy to interpret and is usable by both demographers and economists. In answering the second, she analyzes 1960 and 1970 census data to determine the relative effects of population composition and job structure on levels of employment. One of the important contributions of Sullivan's study is to distinguish between marginal workers and marginal jobs in explaining underutilization. Previous explanations, including the widely used dual market theory, have not stressed this analytic distinction. In addition, her work accounts separately for the various types of marginality and seeks to show the condition of workers who are marginal on more than one count—for example, those who are both young and black, or old and female. A provocative study based on large samples of the U.S. population, this book raises important questions about a critical subject and makes a significant contribution to the theory of underutilization.