Immigrants are sending billions home each year, and getting that money across borders has turned into a massive, entrenched industry

Over the past few centuries, the world has become increasingly globalized. Immigrants are pouring into developed countries like the US, where many jobs pay higher rates than in their home markets. As migrants shuffle around the globe, they have family members and friends back home who they continue to support through cross-border money transfers, called remittances. Three remittance companies — Western Union, MoneyGram, and Ria — have dominated this market for years, operating a combined 1...