Negro Migration During the War by Emmett J. Scott for Carnegie Endowment for International Peace, Oxford University Press pub.

Emmett J. Scott's classic study, Negro Migration During the War, presents data relating to the causes and consequences of migration from South to North during World War I. Only the table of contents and the introduction are included in this pdf; the entire text and transcript are available at books.google.com.

From Chapter II, Causes of the Migration:

The economic motive stands among the foremost reasons for the decision of the group to leave the South. There are several ways of arriving at a conclusion regarding the economic forces. These factors might, for example, be determined by the amount of unemployment or the extent of poverty in a community as registered by the prosperity. These facts are important, but may or may not account wholly for individual action. Except in a few localities of the South there was no actual misery and starvation. Nor is it evident that those who left would have perished from want had they remained. Discontent became more manifest as comparisons were made between the existing state of things at home and a much better state of things elsewhere. It is possible to note in the appeals of the letters a suggestion of a desire simply to improve their living standards so long as there was an opportunity. In the case of some there is expressed a praiseworthy providence for their families; and in others may be found an index to the poverty and hopelessness of their home communities. In this type of migration the old order is strangely reversed. Large numbers of negroes have frequently moved around from State to State and even within the States of the South in search of more remunerative employment. A movement to the West or even about in the South could have proceeded from the same cause, as in the case of the migration to Arkansas and Oklahoma.

Among the immediate economic causes of the migration were the labor depression in the South in 1914 and 1915 and the large decrease in foreign immigration resulting from the World War. Then came the cotton boll weevil in the summers of 1915 and 1916, greatly damaging the cotton crop over considerable area, largely in Louisiana, Mississippi, Alabama, Georgia and Florida, and threatening greatly to unsettle farming conditions in the year 1917. There followed then the cotton price demoralization and the low price of this product during subsequent years. The unusual floods during the summer of 1915 over large sections in practically the same States further aggravated the situation. The negroes, moreover, were generally dissatisfied because' of the continued low wages which obtained in the South in spite of the increasing cost of living. Finally, there was a decided decrease in foreign immigration. The result was a great demand in the North for the labor of the negro at wages such as he had never received.