Steven Johnson in Adjacent Possible:
A few decades ago the Stanford professor Ronald Howard proposed a unit of measure for mortality risk. He called it the “micromort.” One micromort equaled a one-in-one-million chance of dying. Howard was an expert in decision theory, and he had recognized that many of life’s most complicated decisions—particularly medical ones—involved complicated assessments of risk probability. Howard imagined the micromort as a common framework that, for example, a doctor could use with a patient to describe the risks of undergoing a specific procedure—and the risks of not undergoing the procedure.
The standard never really took off, but it has seen something of a revival in the COVID age. There was an op-ed in the Times in May of 2020 that discussed COVID risk using the language of micromorts.