In many countries of West Africa, the alternative financial system of tontine supplements conventional banks. A tontine unites people who informally save up shared money and distribute it to its members on a rotational basis. Mutual trust and the moral obligation to comply with the self-imposed rules are fundamental to this model’s functioning. But what exactly are the strengths of this informal system, which is even practiced in Brooklyn, New York? Is it possible and useful to institutionalize this system (i.e. in microfinance) and still preserve the idea of cooperative sharing? A discussion with the sociologists Papa Sow and Alain Toh will analyze the different facets of tontines, with an emphasis on mutual benefits of cooperative savings.