Selecting the Most Effective Nudge: Evidence from a Large-Scale Experiment on Immunization. Abhijit Banerjee, Arun G. Chandrasekhar, Suresh Dalpath, Esther Duflo, John Floretta, Matthew O. Jackson, Harini Kannan, Francine N. Loza, Anirudh Sankar, Anna Schrimpf, Maheshwor Shrestha. Working