Measuring the impact of campaigning can be difficult. So as a campaigner, how can you tell if you are actually making a difference?

You may have mobilised X thousand people, written Y letters to your local member, or contacted Z journalists to write about your cause. A law might even have been passed or the corporation has stopped doing that bad thing. But how do you know you’ve actually contributed to change? How do you measure impact?

Taren Stinebrickner-Kauffman, the founder of SumOfUs and a keynote speaker at Progress 2015, brings everyone down to earth in a punchy presentation on campaign evaluation. In just 13 minutes, she manages to tell you about how you know nothing (about your organisation’s impact) and how you might go about knowing more: