Malcolm Williams is a Professor and Director of the School of Social Sciences at Cardiff University. Though primarily a sociologist, his work draws on social statistics and philosophy of science. His primary research interests are methodological, particularly probability, causality and the counting of rare and elusive populations. He was the first researcher to use the method of mark- recapture to measure homeless populations. His empirical research has included work on household formation and dissolution, housing need and more recently issues of pedagogy in the teaching of quantitative methods.