This document discusses a study on agricultural production in polygynous households in Burkina Faso. The study finds that while altruism can encourage cooperation, it can also inhibit efficiency by reducing the credibility of punishments. Using data on plot yields, the study finds greater cooperation between co-wives than between wives and husbands in polygynous households, suggesting altruism makes punishment threats less credible. Various robustness checks considering alternative explanations and unobserved factors support the role of altruism in impacting cooperation and efficiency.