There is still another characteristic feature of our economic life, between which and the immigration movement a close and peculiar connection can be traced. This is the frequent recurrence of economic depressions, or crises. The causal relation between these events and the variations in the volume of the immigration current has already been mentioned. There is also a causal relation between these conditions and the fluctuations in the outgoing stream of aliens. This fact has received no little attention of late years, and it has been frequently pointed out that a period of depression in this country is followed by a large exodus of the foreign-born. The popular interpretation of this fact is that this emigration movement serves to mitigate the evils of the crisis by removing a large part of the surplus laborers, until returning prosperity creates a demand for them again. The Italian, who displays the greatest mobility in this regard, has been called the safety valve of our labor market. Thus the movements of our alien population are supposed to be an alleviating force as regards crises. The question arises, however, in this connection, whether there is not a converse causal relation; in other words, whether the conditions of immigration are not, partly responsible for the recurrence of these periods. Professor Commons takes this view of the matter, and in his book, _Races and Immigrants in America_, demonstrates how immigration, instead of helping matters, is really one of the causes of crises. His conclusion is that “immigration intensifies this fatal cycle of ‘booms’ and ‘depressions,’” and “instead of increasing the production of wealth by a steady, healthful growth, joins with other causes to stimulate the feverish overproduction, with its inevitable collapse, that has characterized the industry of America more than that of any other country.”[316] The few pages which Professor Commons devotes to this topic are highly suggestive, and show careful study of the subject. The author, however, at the time this book was written, was handicapped by the lack of data regarding the departures of aliens, which, as we have seen, have since become available. The fact that within the period since the collection of these figures began, the United States has experienced, and recovered from, a severe depression, makes the study of this matter at the present time particularly profitable. First of all, it will be desirable to see just what the facts of immigration and emigration during this period are; then we shall be prepared to attempt their interpretation. The accompanying table (p. 349) gives the number of aliens admitted to and departed from the United States, and the net increase or decrease of population resulting therefrom, by months, from January, 1907, to December, 1910 (with the exception of the figures of departures for the first six months of 1907, which are not available).