One feature of the debate about the idea of a guaranteed annual income — minimum income, basic income, call it what you will — is wide disagreement about what it means, even amongst its supporters.

How high or low would the maximum benefit, paid to those with no other income, be? How sharply or gradually would it be clawed back as earned income rises? Would everyone receive the same universal “demogrant,” to be taxed like other income, or would the amount of the benefit vary with income, as in the “negative income tax” model? And, perhaps most contentious, what existing programs would it replace?

The intersection of these four variables can produce wildly varying cost estimates.