Such things, as it were, slip into the shadow. But economists do place particular emphasis on unpriced public goods such as education and on the fact that it is difficult to measure outputs in this case. For instance, I was once talking with Donald Whitehead, who was defending the GNP as a measure of a country's prosperity. A subsidiary point at issue was whether the total wage bill was a good measure of the amount of productive labour done. He said, yes, it would, but that that would be such an artificial and unlikely thing that it didn't matter.
Income is measured as value-added.
But because it does not feature in the quantifiable way paid labour does it can't fit into calculations , and eludes the standard techniques of economics. Almost inevitably, then, it tends to be overlooked in practice. E.g., everyone who uses the GNP as an estimate of productive labour does so. One can easily overlook matters one is at times quite aware of. I do not know any economist who disagrees with this proposition.