National Development, Mother Tongue Diversity, and the Comparative Study of Nations

Using cross-sectional comparative data, a number of investigators report inverse correlations between mother tongue diversity and various measures of national development. Longitudinal analyses of mother tongue diversity in eight different nations over relatively long periods of time, along with a shorter longitudinal analysis of all European nations, indicate that such correlations are probably void of any causal implications. An analysis of covariance explains why cross-sectional correlations occur between variables that are not dynamically related. In addition to suggesting the need for an alternative perspective on the course of mother tongue diversity, the results have critical implications for some of the most common procedures used in the comparative study of nations.