FOREWORD ) 
the causes and consequences of human migration, comprehensive 
in scope and thorough in detail, can be developed only by co-operative 
efforts, such as the committees of the National Research Council 
and the Social Science Research Council are promoting. Many 
intensive investigations of specific issues, like the present report, 
must be made before we can attain the well-rounded knowledge 
needed as a basis for private opinion and public policy regarding 
migration. 
In accordance with the established procedure of the National 
Bureau, Dr. Jerome's present monograph was submitted in manu- 
seript to our Board of Directors. Criticisms made by members of 
the Board have resulted in various improvements upon the original 
draft. This process of criticism and betterment through which the 
National Bureau's reports pass before publication involves much 
labor upon the part of the Directors;—labor which is mostly self- 
effacing, for almost all the suggestions are incorporated in the text 
before publication. It is but just to state that this volume, like its 
predecessors, owes much more than appears to the acumen, the 
wide and varied experience, of the Directors. 
WesLEYy C. MITCHELL. 
C