In that year another important distinction is made, that between immigrant and nonimmigrant aliens on the inward passage, and emigrant and nonemigrant aliens on the outward passage. Immigrant aliens are those whose place of last permanent residence was in some foreign country, and who are coming here with the intention of residing permanently. Nonimmigrant aliens are of two classes: those whose place of last permanent residence was the United States, but who have been abroad for a short period of time, and those whose place of last permanent residence was in a foreign country, and who are coming to the United States without the intention of residing permanently, including aliens in transit. Departing aliens are classified in a corresponding way. Emigrant aliens are those whose place of last permanent residence was the United States, and who are going abroad with the intention of residing there permanently. Nonemigrant aliens are of two classes: those whose place of last permanent residence was the United States, and who are going abroad for a short visit only, and those whose place of last permanent residence was abroad, but who have been in the United States for a short time, including aliens in transit. In all cases the expressed intention of the alien is regarded as final concerning residence, and an intended future residence of twelve months is considered a permanent residence. The recent reports of the Commissioner General contain tables almost as detailed for departing as for arriving aliens. Thus it is now possible to make an exact reckoning of the net gain or loss in population each year through immigration movements. The classes in which we are particularly interested are naturally the immigrant and emigrant aliens, for they are the only participants in true immigration movements, according to our definition. The others are merely travelers. Yet they are important and interesting travelers, and the modern problems of immigration cannot be thoroughly understood without taking some consideration of them. As for the aliens in transit, they can be quickly disposed of. They are counted as nonimmigrant aliens on their arrival, and nonemigrant aliens at their departure, which is supposed to occur within a period of thirty days. Thus they cancel, and do not in any important way affect the life of the United States. The other class of nonimmigrants and nonemigrants is much more important, for they include a group of aliens who have attracted considerable attention of late—the so-called “birds of passage.” These are, in the strictest sense, aliens who have chosen the United States as their place of permanent residence, but who go back to the old country for brief sojourns on certain occasions. In a broader sense, the birds of passage may also be taken to include aliens whose permanent residence is abroad, but who come to this country for a brief stay.[109]