Factfulness: Ten Reasons We’re Wrong About the World—and Why Things Are Better Than You Think

Hans Rosling's final book (2018), completed with Ola Rosling and Anna Rosling Rönnlund: ten instincts — gap, negativity, straight-line, fear, size, generalization, destiny, single perspective, blame, urgency — that make even experts systematically wrong about global trends (on his thirteen-question quiz, most audiences score worse than chimpanzees choosing at random), each instinct countered with a data habit. At its core is the four-income-level framework that replaces the crude 'developed / developing' split.

Gates made it his 2018 gift to every US college graduate and admitted its framework beat his own: "The framework Hans enunciates is one that took me decades of working in global development to create for myself, and I could have never expressed it in such a clear way. I'm going to try to use this model moving forward." He has used the four-level model ever since.

For founders the transfer is direct: the same instincts corrupt market sizing, user research, and board decks — extrapolating a straight line, generalizing from one segment, blaming a single actor, deciding under manufactured urgency. The checklist is short enough to run in a meeting, and the four-level model is a genuinely better way to segment a global market than rich-world / poor-world.