AN UNUSUAL factory recently began operation near the town of Bogra in Bangladesh. It makes yogurt, fortified with nutrients that poor toddlers often lack, and sweetened with the date molasses the Bangladeshi palate demands. Its marble foundation stone was signed by Zinedine Zidane, one of the world's greatest footballers, and its owners think the factory will inspire a nobler breed of capitalism.

The factory traces its origins to a 2005 meeting in a Paris restaurant between the chief executive of Groupe Danone, a French multinational, and Muhammad Yunus, founder of Grameen Bank, who won the Nobel peace prize in 2006 for championing the cause of microcredit. In his new book, Mr Yunus describes how Grameen and Danone agreed on a joint venture to sell nutritious food to the poor. It is a wholesome tale of French businessmen finding meaning in their lives, and Bangladeshi children enjoying something better than rice gruel to eat. But Mr Yunus also smothers the story in molasses, making claims about the originality and profundity of the enterprise that are simply too rich to take.

The yogurt factory is what Mr Yunus calls a “social business”: a new concept, he argues, that has the potential to ease poverty and redeem capitalism. A social business has two distinguishing features. It offers worthwhile products that poor people are willing to pay for. And the profits it makes are reinvested in the enterprise, not distributed to its owners. A social business is a “zero-loss, zero-dividend” venture, as Mr Yunus puts it.

Mr Yunus foresees social businesses bringing clean water, renewable energy and health insurance to the impoverished masses. Let's hope so. But non-profit corporations of various kinds are hardly new. America alone has about 1.4m of them by one count, including hospitals and universities, if not yogurt factories, that charge low rates to the poor and are forbidden from distributing their profits to owners.

Mr Yunus might argue that these non-profits rely on donors, not investors. But the difference is more apparent than real. A social business promises to repay its backers' money after, say, five years, but with a 0% return. This is just another way of asking investors to donate the interest they would have received had they left their money in the bank instead.

However tasty and nutritious the yogurt they eat, the poor will not consume their way out of poverty. To escape, they must find a way to make more money. This simple truth is repeated by Paul Polak, the founder of International Development Enterprises (IDE), in “Out of Poverty”, his wise and engaging new book.

Most people in extreme poverty work on small, rain-fed farms, growing staple grains partly for their own consumption. These crops provide a family's best guarantee of survival, but no more than that. To break free of this unhappy equilibrium, farmers must set aside a portion of their land to grow cash crops in the dry season, when they fetch a high price. IDE helps farmers gain access to the irrigation, fertiliser and markets they need to make that strategy work.

Whereas most people find poverty distressing, Mr Polak also finds it endlessly fascinating. He is happiest muddying his boots on thousands of one-acre farms, marching up hillsides to inspect irrigation tanks, or loitering in a market, measuring the shelf-space that stallholders devote to different vegetables. He scorns poverty experts who profess to know more about the subject than the people who live it. A former psychiatrist, he listens intently to poor people before allowing his mind to run over with tricks, gambits and contraptions that might help them.

He tries to weave his book together with the story of Krishna Bahadur Thapa, a Nepali farmer who escaped poverty thanks to some of the techniques and strategies Mr Polak advocates. For example, drip irrigation allowed Mr Thapa to grow cucumbers out of season, when they sold for three times their normal price. He invested the proceeds of his farm in a better home, schooling for his children and a more varied diet. Mr Thapa would not have described his profitable endeavours as a social business. But his story makes one wonder if honest enterprise really needs a new epithet to ennoble it.