Millions of Americans are currently without health insurance because they can’t afford it. One in seven Americans are without health insurance because insurers can’t afford them. Uninsurable Americans are without insurance because they are already sick with heart disease, cancer, diabetes, and other pre-existing conditions that make insurers deny coverage. Why not charge those people more if they’re willing to pay? Nathaniel Hendren, a graduating Ph.D. student at MIT, conducted a study and has a theory. People with pre-existing conditions have a better idea of what their care will cost in the future, thus giving them a better position to weigh the numbers. Insurers are in a losing proposition when the only customers who enroll are the ones who plan to pursue aggressive and expensive treatments.