§ 1. In the two preceding chapters nothing was said about the possible reactions which the changes we have been contemplating may have on the numbers of the population. This omission must now be remedied. To the broad conclusions which were reached relating respectively to the size and distribution of the national dividend, it may be objected that an increase in the income enjoyed by any group causes its numbers to increase until income per head is again reduced to its old amount, and, therefore, that it leads to no lasting benefit. In practice this argument is most often used about the effects of an increase in the income of manual workers; and it is, of course, much more plausible in this field than in any other. It will, therefore, be enough to examine this aspect of it. I shall consider it first from the point of view of the whole world, or of a single country imagined, for the purposes of the argument, to be isolated, and afterwards shall inquire how far the results achieved need to be modified for a single country constituting one among the associated family of modern nations. In the argument to be developed under these two heads it must be understood that the additions to the income of wage-earners that we have in mind do not include additions brought about by the offer, on behalf of the State, of deliberate and overt bounties upon the acquisition of large families. Under the old Poor Law in the United Kingdom bounties were, in effect, given; our present income-tax law acts in a slight degree in the same sense; and in a law passed in France 1 99shortly before the war a similar policy was adopted. This class of addition to the income of the poor has, of course, a tendency to augment population, and, in some practical problems, the point is of importance. For the present, however, we are concerned with additions that do not offer a special differential inducement to the begetting of children.