Book excerpt: Longtime Urban Institute researcher Martha Burt and her co-authors provide an in-depth analysis of homelessness, exploring issues such as how many homeless people there are in America, where they are, why they became homeless, how long their homelessness lasts, the different ways programs in different communities are helping the homeless, and how policymakers have approached the problem. Finally, they consider what societies may be willing to do reduce the probability that their members will become homeless. c. Book News Inc.