> For economists, efficiency is simply that goods should be created where the surroundings are best suited for it - first described by David Ricardo in the 19th century. E.g. Cotton should be planted where there is the most fertile soil etc.

This seems slightly off to me. Cotton can be grown more efficiently (in the usual sense of less cost per unit return) in some climates than others. But the economy as a whole may be more efficient if cotton is grown exclusively in subpar-for-cotton areas; perhaps the ideal-for-cotton areas are needed for another crop.

As I understand it, "efficiency" in economics will refer to one of two ideas:

1. Small deadweight losses. The smaller they are, the more efficient the economy is.

2. Pareto efficiency. (That is, the economy is efficient, in this sense, if there is no reallocation of resources that makes somebody better off without making anyone worse off.)