In regard to the second assumption—that a smaller labor supply would not have been offset by an increase in invention—we are again confronted with an impossibility of proof, one way or the other. The economists tell us that one of the great incentives to invention is a scarcity of labor, and also that many of the greatest inventions have been made by men who are working daily with machines, and consequently are in a position to discover improvements that may be made. There is at least some reasonable basis for the belief that if the absence of immigration to this country had resulted in a smaller laboring force, the greater pressure on employers to secure machinery, and the greater intelligence of the machine worker, would together have brought about such a betterment of labor-saving machinery as would have resulted in a total production equal to what we have actually witnessed. It is inconceivable that in America, of all countries, any needed work should have to be neglected because of the lack of a foreign labor element, or because of a shortage of labor in general.[312] It is hard to see how in a nation the majority of whose citizens are healthy and intelligent there can be any real shortage of labor. What there can be, is a shortage of labor _at a given wage_. In a prosperous community there may be industries into which a sufficient number of laborers will not go, at the wages which the promoters are originally willing to pay. But if there is an actual social need for those industries, wages will rise to a point high enough to attract a sufficient number of workers, however irksome or disagreeable the employment. No self-respecting community ought to expect industries to be carried on within its borders for which it is not willing to pay such a price as will enable the workers to subsist in reasonable comfort and decency. If there are any industries carried on in the United States which, in the absence of a foreign labor supply, would have to be abandoned, because the native-born laborers or their children would refuse to go into them, it simply means that society is not yet ready to pay a fit price for the products of those industries.