The most common usage in macroeconomics would be the national income accounting, where it is income streams owing to title to a natural resource, and the national income accounts make no judgement that one of the four sources of factor incomes is earned and another unearned ... in the national income accounts, all factor income is earned, and unearned income involves transfers that come from the taxes that introduce a wedge between earned and disposable income.
On the other hand, the neoclassical rent is unearned income due to the scarcity value irrespective of whether it is due to a claim on a natural resource or on productive equipment ... the rent that is incorporated into the purchase price for the strategic resource can just as easily be the rent on a taxi medallion when the number of licensed cabs has been allowed to fall behind the extent of the market as the rent on a favorable site for a wind farm.
And, after all, neoclassical economics is, after all, quite passé, even among marginalist economists. I've been accused of being a Marxist, yet while Harpo's my favourite, it's Groucho I'm always quoting. Odd, that.
