What Do We (And Others) Mean by 'The Terms of Trade'?

I explore how the concept of “the terms of trade” has been used since it was coined by Marshall. Early writers (Taussig, Viner, Dorrance) constructed variations on the relative price of traded goods that Marshall was concerned with, but most of these variations have been left behind in modern uses of the term, which today almost always refer to a relative price of exports and imports. However, when authors have wanted to identify the terms of...