For instance, in economic theory we find
that the allocation of factors of production between different
uses is determined by the price mechanism. The price
of factor A becomes higher in X than in Y. As a result,
A moves from Y to X until the difference between the
prices in X and Y, except in so far as it compensates for
other differential advantages, disappears. Yet in the real
world, we find that there are many areas where this does
not apply. If a workman moves from department T to
department X, he does not go because of a change in relative
prices, but because he is ordered to do so.