Abstract
The lower fertility of the Indian-speaking parts of Bolivia, Ecuador and Peru compared with the Spanish-speaking parts of these nations has been the topic of several previous articles in this journal. In last year's journal William H. James argued that higher altitude was the chief cause of this reduced fertility level, whereas D. M. Heer has earlier argued that it might be accounted for by higher proportions of women in the labour force. James's data and Heer's further computations suggest that James's explanation has substantially more merit than that originally advanced by Heer.

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