DOI link for Labour productivity
Labour productivity book
This concentration on physical productivity means that our focus must be one industry at a time. We cannot yet consider the economy as a whole since, without introducing prices or other means of valuation, we lack any scale by which we could measure the aggregate product. The total product of the economy comprises a heterogeneous mixture of goods, in technical terms a vector or list of numbers, such as
(x tons of steel, y cars, z barrels of oil, . . .)
Vectors are a means of describing positions in multi-dimensional space. To get an unitary measure of change in production you need to render these specific quantities comparable, by mapping them onto a scalar quantity such as monetary value. For the moment we consider one product at a time, and the natural units of that product will provide us with our scale.