Cover image: Suburban development in Howard County, MD. Spatial fragmentation as a function of distance from an urban center follows a parabolic curve, as the highly developed center gives way to countryside. Comparing the geography of the state of Maryland in 1973 and 2000, Irwin and Bockstael find that the parabolic curve has become higher and steeper, marking a significant increase in sprawl. See the article on pages 20672–20677. Image courtesy of Elena Irwin.