[2] In measuring the cost of goods in labor, in Chapters IV and V, we disentangled from the amount of goods which is the joint product of labor and capital, the part which is attributable to labor only. The mode of doing this is there more fully stated. The old and crude method of using a labor standard of value--which assumes that the product of a unit of labor _aided by capital_ will always buy the product of another unit of labor _aided by capital_--we must take _all pains_ to avoid. In connection with the cost in labor of different articles it is to be remembered that in agriculture the effect of improvements of method may not always suffice to counteract the working of the so-called law of diminishing returns, which insures, with agricultural science in a given state of advancement, smaller products per capita when there are more men on a given area. That this influence should preponderate over that of improved processes requires that population should increase with a degree of rapidity which may or may not be maintained. CHAPTER XIII THE LIMITS OF AN ECONOMIC SOCIETY When we try to establish a standard to which wages generally tend to conform, the question arises how much of the earth we have in view. Is there a rate at which the pay of labor in Europe, Asia, Africa, Australia, and America tends to settle and remain? Is there a common rate of interest that is normal in all these grand divisions, and are there also general standards of value for goods which govern their prices in all the markets of the world? If there are no such standards having universal validity, are there any that are valid within single geographical divisions? On what principle can we divide the earth into sections for economic purposes? These are some of the questions which must be answered if a theory of distribution is to have any definiteness of meaning, and they arise whenever we try to establish a static standard of any kind. If we talk about natural wages, we must know in how much of the world they are natural. The questions become even more urgent when we try to solve dynamic problems. We shall have to determine the effects of an influx of labor into the economic society we are studying; but does this mean an increase of population in the world as a whole? Does an influx of capital have a similar comprehensive meaning, and does an improvement in the method of producing some commodity mean a change in the mode of making it in every part of the world where it is produced at all? We need to know how extensive the society is whose activities we are examining.