Society & Culture / Social Issues / Demographics & Aging

Why Migration Predictions Always Fail (And the Secret Math That Fixes It)

Towards Bayesian Model-Based Demography

Jakub Bijak

Demographers have a dirty secret: almost every traditional migration model completely fails. While birth and death rates follow steady biological patterns, migration is pure human chaos fueled by fear, borders, and fake news. Based on the groundbreaking book Towards Bayesian Model-Based Demography by leading demographer Jakub Bijak and his research collective, this presentation breaks down a radical shift in social science: abandoning rigid spreadsheets and simulating living, breathing human decisions. Slide 1: Traditional data is blind. Census records only tell you who arrived yesterday. They tell you nothing about who runs tomorrow. Slide 2: The rumor effect. Refugees do not follow optimal highway maps. They follow whispered rumors, smartphone group chats, and perceived danger. A single rumor can reroute thousands of people overnight. Slide 3: Creating digital human guinea pigs. Forget aggregate curves. Scientists now build computer agents programmed with human cognitive biases. These digital agents get scared, share bad advice, and get lost just like real people. Slide 4: The Bayesian reality check. Instead of pretending to know the future, the model continuously updates its beliefs as new clues appear. It marries cold computation with raw behavioral psychology. Slide 5: The ultimate payoff. For the first time, policy makers can stress-test humanitarian routes before a crisis explodes on the news. Explore how computational psychology and Bayesian modeling are turning the most unpredictable human movement into measurable science.