There's a new way to change the world, writes social entrepreneur Michel Gelobter. It's called the lean startup - but it's not just for new ventures. It's been revolutionizing businesses of all ages for years, and Gelobter shows it can have the same transformative impact on the social sector.

Traditionally, an entrepreneur develops a detailed plan, finds money to fund it, and then pursues it to its conclusion. But conditions can change drastically at any point - you can end up locked into a process based on now-obsolete assumptions. The lean startup is all about agility and flexibility. Its mantra is "build, measure, learn": create small, experimental initiatives, get real-world feedback on them quickly, and use that data to identify what works and discard what doesn't. And then test some more.

Gelobter explains exactly how nonprofits and advocacy organizations can adapt lean startup concepts to their unique circumstances. He offers dozens of real-world examples: an established homelessness group whose data analysis showed that reducing a single overlooked metric could get many more people off the street; a technology-based literacy startup that used lean techniques to reach two million children in two years when a more traditional program took 15; and many others. The standard approach wastes time and money - the lean startup promises to help social sector organizations vastly increase the good they do.