Professor Bales' research has advanced a new tool for estimating the true extent of modern slavery and trafficking across the world. His adaptation of the Multiple Systems Estimation (MSE) technique, first pioneered for slavery with Sir Bernard Silverman in 2014 for the UK, is helping to provide the first reliable estimates of modern slavery. National and global slavery estimates, including Walk Free's Global Slavery Index on which Professor Bales collaborates, are the baseline against which the United Nations can measure progress towards its Sustainable Development Goal of ending slavery by 2030. His ESRC/AHRC-funded work has enabled him to carry out further applications of MSE, particularly in a regional US context.