BUSINESSES avidly mine data to improve their efficiency. Non-profit groups have plenty of information, too. But they can rarely afford to hire number-crunchers. Now a bunch of philanthropic geeks at DataKind, a New York-based charity, are helping other do-gooders work more productively and quantify their achievements for donors, who like to see that their money is well spent. A typical DataKind two-day "hackathon" last month in London attracted 50 people who worked in three teams. One pored over the records of Place2Be, which offers counselling to troubled schoolchildren. Crunching the data showed that boys tend to respond better than girls, though girls who lived with only their fathers showed the biggest improvements of all. The charity did not know that. The expertise is far beyond what is available to a typical charity. The small-talk among the volunteers was of dizzyingly complex statistical and artificial-intelligence techniques. Volunteers included an analyst at Teradata, a data-analytics firm. Around 20 employees attended from Aimia, a firm that mines data from consumer-loyalty programs. In a previous hackathon in San Francisco, DataKind volunteers analysed the data from Mobilising Health, a non-profit group that connects rural patients in India with doctors in cities that are usually many hours away. Volunteers record symptoms and relay them by cellphones. The doctors then may prescribe drugs or recommend a hospital visit. The charity wanted to use the many months" worth of accumulated text messages to evaluate the medics" performance. Thanks to DataKind the charity was able to rejig the system to take more account of urgency and to direct requests to the most responsive doctors. Thomas Levine, a data scientist at ScraperWiki, a provider of data-processing services, says he has attended DataKind events out of altruism but also for education. Would anyone care to measure that benefit?