If the base of a population pyramid has been narrowing continuously for twenty years, which future change is likely?

Correct answer: New cohorts entering working ages may become smaller

The base of a population pyramid represents the youngest age groups. If it becomes narrower continuously for twenty years, fewer children have been entering each successive cohort, usually because fertility has declined. After enough time passes, these smaller cohorts move upward through the age structure and begin to enter working ages. Therefore, the number of new people entering the labour force may become smaller, making option A correct.

This conclusion concerns the size of future cohorts, not an exact prediction of employment or total population. Migration, mortality, and changes in fertility could modify the final result, but the cohort effect remains important. A narrowing base does not imply that child population must double or that fertility will become very high. Elderly dependency may eventually rise as smaller cohorts replace larger ones, so it certainly cannot be said to decrease. Thus option A is the most defensible forecast.