Despite it being a huge humanitarian problem, why is HIV/AIDS the wrong disease to attack in Africa even if the objective is lowering overall HIV prevalence? What do neuroscience and economics have in common? If monthly gym members pay higher fees than annual gym members for the option to cancel each month, why are they much more likely to stay enrolled beyond one year than users committing for a year? If the price for an average meal has stayed relatively stable, how can restaurants afford offering increasingly bigger food portions to their customers?