On paper, Arcelia looks like a poor-but-average Mexican town. It sits in Guerrero, Mexico 's second-poorest state.  Official data gives it a score of 0.714 — firmly in the "high development" band on the  United Nations' Human Development Index (HDI).    Then a satellite looks at Arcelia. Using artificial intelligence to analyze what it sees, it returns a lower score of 0.617.  By the UN's own classification, that is no longer high but medium development — a different development tier and a