What the Numbers Say: A Digit-Based Test for Election Fraud Using New Data from Nigeria

Abstract

Is it possible to detect manipulation by looking at electoral returns only? Drawing on work in psychology, we exploit individuals’ biases in generating numbers to highlight suspicious digit patterns in reported vote counts. First, we show that fair election procedures produce returns where last digits occur with equal frequency, but lab experiments indicate that individuals tend to favor small numbers, even when subjects have incentives to properly randomize. Second, individuals underestimate the likelihood of digit repetition in sequences of random integers, so we should observe relatively fewer instances of repeated numbers in manipulated vote tallies. Third, lab experiments demonstrate a strong preference for adjacent digits, suggesting that non-adjacent digits should appear with lower frequency on fraudulent return sheets. We test for deviations in digit patterns using data from Sweden’s 2002 parliamentary election and previously unavailable results from Nigeria’s 2003 presidential election and nd strong evidence that manipulation occurred in Nigeria.