Related works CR Della vigna and Malmendier(2004, QJE): contract design with time inconsistency(monopoly firm CR Heidhues and Koszegi(2010, AER): credit contract with time inconsistency(competitive firm) CR Basu(2011, AEJ-Micro): individuals join rotational savings and credit associations (roscas)to fund repeated purchases of nondivisible goods without defect even when there is no punishment, roscas serves a commitment device  DellaVigna and Malmendier (2004, QJE): contract design with time inconsistency (monopoly firm)  Heidhues and Kőszegi (2010, AER): credit contract with time inconsistency (competitive firm)  Basu (2011, AEJ-Micro): individuals join rotational savings and credit associations (roscas) to fund repeated purchases of nondivisible goods without defect even when there is no punishment, roscas serves a commitment device Related Works