The Course of Mother-Tongue Diversity in Nations

The course of mother-tongue diversity is abstracted from longitudinal data gathered for 35 nations. The Greenberg A index is used to measure diversity in each nation, and the magnitude of change is determined through a procedure proposed by Coleman. Diversity declines over time in the majority of cases, but there is considerable variation between nations and in 14 cases diversity has increased. Accordingly, various national characteristics are considered to see whether they help account for the magnitude and direction of change observed among nations. Two factors, the spatial isolation of language groups and official educational policies, have fairly high correlations with changes in diversity. In addition, several geopolitical factors have affected diversity change in the past: age of nation, boundary changes, forced population movements, and World War II. Two specially puzzling results are the comparatively rapid rate of mother-tongue change in the United States and the failure of national development to have much bearing on the course of mother-tongue diversity. A theoreticl approach accounting for these events is described.