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THE AMERICAN JOURNAL OF SOCIOLOGY

would not easily be discovered, namely, the curve of 1900 is slightly less irregular than the curve of 1890. Very slightly, but perceptibly, it is nearer the straight line which would express the divergence of nationalities from the native-born of native par-

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Fig. 3. — Nationalities: Frequency Curve of Resemblance Positions, 1890.

ents, if each successive step of divergence were equal to the step preceding, and if each nationality were represented in our popu- lation by the same number of individuals. This circumstance suggests a question: Is our population becoming slightly less

Fig. 4. — Nationalities: Frequency Curve of Resemblance Positions, 1900.

heterogeneous, contrary to the prevailing belief? We shall pres- ently see that it is.

The curves of frequency show the positions of the modes. A multi-modal curve, as all statisticians understand, indicates a

compound group, or one made up of two or more kinds of units.