The study presented in this book began as dissertation research. Over the years many friends and colleagues have helped and encouraged me in a variety of ways. I am indebted to my dissertation committee at Northwestern University, who guided me through the research process as carefully and painlessly as any student might hope. Robert Nelson, my committee chair and graduate studies advisor, managed to find an almost impossible balance between helping to open my eyes as a sociologist and allowing my eyes to wander to new and interesting phenomena to examine. Few graduate advisors are as willing to let students define their own research topics and goals as Bob is. It is hoped that Bob's positive influence upon me is apparent throughout this book.
Arthur Stinchcomb and Bernard Beck, the other members of my dissertation committee, also contributed to this work in distinct ways. Art provided a constant stream of critical comments that forced me to consider new issues and improve my work at all stages of the research and writing process. Bernie diligently listened to numerous stories and potential interpretations of data on a regular basis. The long hours I spent with Bernie were immensely