Score contribution per author:
α: calibrated so average coauthorship-adjusted count equals average raw count
Each year two million secondary school students across West Africa sit coordinated exams. Pass rates fluctuate enormously, fueling speculation about cheating and short-term policy changes. To investigate these hypotheses, we construct hybrid exams containing items spanning 2011–2019 and administer these to 4,380 students. Exam difficulty alone explains 80 percent of pass rate fluctuations in Ghana, while additional factors remain influential in Nigeria and elsewhere. Half of the candidates who failed mathematics in 2015 would have passed in 2019. Model-based estimates imply that improving exam comparability would increase the Mincerian return to skills among secondary school graduates by six percentage points.