SEMAINE D'ÉTUDE SUR LE ROLE DE L’ANALYSE ECONOMETRIQUE ETC. 255

The homogeneity of the production function enables us tu
go over to per-unit-of-labor-force concepts. Calling the unit
of labor force briefly a « worker », let x denote consumption
per worker, y ditto net investment, z ditto capital stock, and

(9)

output per worker. Since we then have

the feasible set in the space of per-worker variables +

romes

(ro) (10a
) (IOd.€

Ver

The term Jz represents the (net) investment needed if one
wants merely to supply the growing labor force with capital
at the existing ratio of capital per worker.
To be specific we shall call a path (x, z,) satisfying (10)
attainable (for the given z,), and use the term feasible path ir
the wider sense of a path attainable for some z,>o0.
It is implied in (7 e) that f(z) is strictly concave

{!) A strictlv concave function is one that is strictly « above » all its
rhorde

41 Koopmans - pag. 1)