The Big Ditch creatively brings economic history to the study of imperialism and sheds new light on the Panama Canal's impact as well as the decision of the United States to relinquish control over it in the 1970s. Although the Panama Canal has enjoyed something of a renaissance of interest in recent years (see, for example, Adam Clymer's Drawing the Line at the Big Ditch [2008], Julie Greene's The Canal Builders[2009], John Lindsay-Poland's Emperors in the Jungle [2003], Alexander Missal's Seaway to the Future [2008], and Ana Patricia Rodríguez's Dividing the Isthmus [2009]), its economic history has received relatively little attention. Noel Maurer and Carlos Yu rely on the economic historian Robert Fogel's idea of calculating social savings by comparing a given project to unchosen options. The key question, they note, was who precisely would benefit from the spectacular geography of Panama and its canal. Furthermore, they examine how those benefits changed over time. There is much rich analysis in this book, but three conclusions emerge as especially significant. First, Maurer and Yu argue that the canal generated major social savings for the United States during the first decades after construction, which benefitted both American producers and consumers. Second, they show powerfully that the canal brought little economic reward to the Republic of Panama. Indeed, they note, “U.S. policy went out of its way to deny Panamanians the benefits of having the canal on their soil” (p. 321). The commissary system, for example, monopolized most of the business that supported the canal's construction and maintenance. Although the canal project resulted in major health and sanitation improvements for the people of Panama, even those were paid for by Panama. Third, The Big Ditch persuasively shows the key role played by economics in the U.S. decision to transfer control of the canal to Panama: it occurred when “the economic benefits from ownership of the canal … sufficiently declined” (p. 11). Three factors generated this economic decline: the interstate system, the rise of the Pacific Coast as a market, and the reduced cost of railroad freight. As these factors combined with rising Panamanian nationalism during the post–World War II decades, the necessity of the transfer became increasingly obvious.