Some things are really hard to measure with numbers alone, like how deprived a neighbourhood is or how widespread a social problem might be. My comparative judgement work asks experts to look at two areas side by side and say which one is worse. By collecting lots of these simple comparisons, I can use statistical models to build a full ranking and create maps that show where problems are most serious. This approach has been used to map forced marriage across England and urban deprivation in Dar es Salaam, Tanzania. Local councils have used these maps to train their staff, and MPs have asked questions in Parliament based on this research.