This report outlines the importance and promise of serving low- and lower-middle-income (LMI) populations -- essentially, the groups situated between the very bottom of the pyramid and the existing middle class. As we detail herein, LMI populations have huge unmet needs and face quite a bit of instability -- challenges that can be addressed by innovative business models. We believe companies serving this demographic represent an under-tapped opportunity, both for financial returns and for outsized impact. The LMI segment represents a major market opportunity. For example, in Latin America and the Caribbean, the purchasing power of the LMI population is estimated at $405B. In South Asia, it is estimated at $483B.