Elizabeth Pisani, visiting senior research fellow at King's College London, collects data on sex workers and injecting drug users in low and middle income countries.
For years she has been sharing her data, and joins us to explain why she went from being protective of her research to to making it freely available - and talk about some of the practicalities of keeping participants anonymous.
Read the full analysis:
http://www.bmj.com/content/355/bmj.i5295