Few books have influenced the interest group field more than Mancur Olson's The Logic of Collective Action (1965). In this seminal book, Olson undermined pluralist thinking by arguing that broad interests were very difficult to organize and, thus, those organizations that lobbied as a by-product of resources aggregated for other reasons were advantaged in the political process. To cut to the chase, corporations, trade groups, and professional associations could organize easily while citizen groups were largely doomed by the collective-action problem.

In his new book, Strength in Numbers, Gunnar Trumbull tells readers that Olson was wrong. And Trumbull is right—Olson was wrong on this count. One has to look no further than the success of citizen groups in the United States to recognize that the collective-action problem is not an insurmountable challenge to organizing. Trumbull's primary contributions are explaining why this is the case and demonstrating how effective citizen group advocacy has become common across Western democracies.

Trumbull focuses on the representation of consumer interests, primarily in Western Europe, but he also includes the United States and Japan. He uses the comparative case study approach as his methodology, and the specific issues he chose vary across many different substantive areas, including agriculture, pharmaceuticals, and consumer credit. The lack of a precise time frame makes his analysis a bit unwieldy, but the scope of the research is impressive, and one finishes this book with a broad understanding of consumer policy in the latter half of the twentieth century.

Trumbull's attack on Olson's formal theory is based on the mobilization of what he calls “diffuse” interests. The consumer groups in the countries studied not only rose to oppose business interests but also have had a reasonable amount of success in winning pro-consumer policy decisions from their governments. Indeed, the author finds that it is relatively rare that concentrated interests (business) attained policy outcomes “that directly undercut more diffuse economic interests” (p. 6).

Beyond the willingness of consumers to mobilize, Trumbull cites three other reasons why consumer groups were relatively successful in their advocacy. First, he documents the importance of what he calls “narratives.” These policy frames structure debate. Is consumer credit an issue of access to credit for ordinary citizens, or is it an issue revolving around the protection of consumers from unsavory practices by lenders? If one or the other becomes the dominant narrative, it will make a difference in the policy alternatives that stand at the heart of debate by policymakers.

Second, he emphasizes legitimacy. By itself, business may well be seen as pursuing selfish interests. Consumers have an inherent advantage in this respect, but Trumbull says that the real advantage comes with “legitimacy coalitions.” Consumer groups and business organizations greatly enhance their legitimacy before policymakers and the broader public when they work together. A third and related point is that consumer interests can be greatly aided by government. When agencies or leading legislators become advocates for consumer interests, the balance of power is altered.

The weakness in Trumbull's argument is his evidence on consumer mobilization. For each country he cites the activity of consumer groups, but most seem small, and across the Western democracies, the organizing of rank-and-file consumers appears modest. The author does little to distinguish between organizations that are able to support themselves without significant memberships (such as Ralph Nader's organizations) and those that truly mobilize followers. More broadly, he fails to get inside these groups, and unfortunately, their means of organization, the level of involvement of their rank and file, and their lobbying are not adequately discussed. An irony of Strength in Numbers is that if Trumbull had utilized environmental mobilization instead of consumer organizing, he would have dealt a much more decisive refutation to Olson's collective-action theory. In the Western democracies, there truly has been broad mobilization of citizens around environmental issues.

Trumbull is much stronger on the role of agencies and legislators. By bringing the state in, he paints a full portrait of policymaking on consumer issues, and he is convincing in showing how government can counterbalance the energetic advocacy of business groups. This part of his explanation takes on added importance with the rise of the European Union. Most of his cases took place before the formation of the EU, but his broad argument is easily adapted to this powerful regional government.

A second theme in the book is the relationship of consumer advocacy to agency capture. “Capture” is a rather categorical term, and contemporary interest-group scholars tend to focus instead on differentials in access to agencies and relative degrees of influence. As such, it seemed as though Trumbull was more interested in addressing a much earlier cohort of political scientists, such as Marver Bernstein, who made the case for agency capture. In one chapter devoted to testing whether capture by business still holds sway, Trumbull analyzes the pharmaceutical industry. Given the huge impact of drug pricing on government budgets, it would have been quite surprising if he had found anything other than limits on industry influence. Agencies and government leaders are well aware that letting industry have its way could quickly bankrupt their country. In short, a more carefully calibrated test would have served Trumbull much more effectively.

Despite these shortcomings, there is much to admire in Strength in Numbers. The comparative policy analysis is rich and informative, and the book offers a great deal of insight into policymaking on consumer affairs. Trumbull is clearly knowledgeable about the governments of the many countries he includes, and his broad reach is a real strength. In his book he has taken on an icon of social science and he has shown little hesitation in making the case that the Olson theory is fundamentally wrong, rather than being just modestly imprecise or needing only a bit of adjusting.

Given the seriousness of the flaws in Olson's theory, why has it endured so? Trumbull tells us that the “Lazarus-like qualities” of Olson's book make for “a fascinating case study in the sociology of knowledge” (p. 207). He concludes that the durability of Olson's work “is a testimony to the allure of game theory as a tractable model of social organization” (p. 207). At least as far as it applies to interest groups, this seems like a fair indictment. The elegance of Olson's theory simply is not supported by the evidence.