The Idealist: Jeffrey Sachs and the Quest to End Poverty, by Nina Munk, Doubleday, 260 pages, $26.95

Jeffrey Sachs' formula for ending poverty was appealingly simple. All the problems of poverty, the famous Columbia University economist argued, had discrete technological fixes. Bed nets could prevent malaria-spreading mosquito bites. Wells could provide clean water. Hospitals could treat curable diseases. Fertilizer could increase yields of food crops.

Ending poverty, therefore, was just a matter of raising enough money to pay for the right combination of known technical solutions to poor people's problems. Sachs would provide a slam-dunk demonstration project by deploying these comprehensive tech fixes in a dozen or so "Millennium Villages" in Africa. Success would build upon success, and advocacy money would flow, until poverty was eliminated from the poorest continent.

The Idealist, Nina Munk's brilliant book on Sachs' anti-poverty efforts, chronicles how his dream fell far short of reality. Munk, a contributing editor at Vanity Fair, follows Sachs around as he supervises the experiment. She also goes out on her own to the Millennium Villages, especially Dertu, in the ethnic Somali region of Kenya's arid north, and the more centrally located settlement of Ruhiira, Uganda. What she finds in these villages reveals much about the future of the aid and development debate.

Sachs' technical fixes frequently turned out to be anything but simple. The saga of Dertu's wells is illustrative. Ahmed Mohamed, the local man in charge of the effort, discovers that he needs to order a crucial part for a generator that powers the wells. The piece takes four months to arrive, and then nobody knows how to install it. Eventually a distant mechanic arrives at great expense. A couple of years later, Munk returns to find Mohamed struggling with the same issues: The wells have broken down again, the parts are lacking, and nobody knows how to fix the problem.

A little more than a year after that, the wells are up and running again, and the Millennium Villages blog celebrates Dertu as having "the most reliable water supply within the region." Yet by 2011 the wells have run completely dry due to a drought—a not-uncommon occurrence in the arid region.

Such examples multiply in Munk's book, showing that purely technological answers to poverty fall well short of Sachs' promises. It turns out that technology does not implement itself; it requires the assistance of real people subject to widely varying incentives and constraints in complex social and political systems.

Munk relates successes as well as failures. Sachs' project spent $1.2 million on health in Ruhiira, hiring two doctors and 13 midwives. Now many fewer mothers in Ruhiira are left to their own resources to give birth, and the prevalence of malaria has fallen dramatically. But too often, the failures seem to offset these small victories. In recent years, Munk has found herself chronicling a rising chorus of criticism. Three months before the release of Munk's book, Foreign Policy published a harsh critique of the project, offering negative verdicts from an impressive roster of experts in the development field.

This final tide of criticism of Sachs' vision came from an unlikely source. Like Al Capone going to jail for tax evasion, Sachs' promise that aid would deliver an end to poverty wound up being convicted on a lesser charge: shoddy evaluation procedures. To declare that the experiments had been a success, any positive trends in the Millennium Villages should have been measured against Africa-wide trends in health, access to clean water, and overall development. But because of the way Sachs set up the project, this comparison could not be done reliably. For example, his team had not collected any data on any other similar villages, which would have made it possible to contrast what happens with and without the Millennium Villages treatment and cash.

New York University economist Jonathan Morduch told Foreign Policy that Sachs' "big-package approach is an anachronism relative to the ideas that development economists have gravitated toward.â€¦Today's typical projects are narrow, easier to evaluate, and pitched as part of a layering of independent interventions. A sanitation project here. A school intervention there." Sachs' set-up failed to deliver the kind of evaluation-friendly projects that today's development economists prefer-targeted interventions that show very focused (and relatively modest) results.

Sachs' true objective for the Millennium Villages was much grander. He hoped to show that properly delivered aid could bring about the end of poverty. His critics rarely mention this aspect of his work. The notion of such sweeping change is apparently so implausible to today's development economists that they do not consider it worth refuting. The big aid debate that Sachs initiated is already over.

We can now see that aid and development are two distinct topics that should each have their own separate debates. If today's development economists talk only about what can be tested with a small randomized experiment, they confine themselves to the small aid conversation and leave the big development discussion to others, too often the types of advocates who appeal to anecdotes, prejudice, and partisanship. It would be much better to confront the big issues, such as the role of political and economic freedom in achieving development.

In 2005 I wrote a negative review of Sachs' book The End of Poverty, and I became identified for years afterward (with rising unwillingness) as the antithesis to Sachs' thesis, a polarized side in a never-ending debate—Aid can end poverty! No, it can't!—that played itself out in dueling books, blogs, media quotes, and syllabi. Eight and a half years later, I take no pleasure in the defeat of Sachs' big ideas, especially since this failure involves the suffering of those who were the subjects of the Millennium Villages experiment.

Sachs does deserve some positive recognition: He was and is a very gifted and hard-working advocate for those who have not yet benefited from the considerable progress that has happened as a result of development. But his idea that aid could rapidly bring the end of poverty was wrong. It's time to move on.