The latest United Nations projection for world population reflects the significant demographic changes likely to occur in different parts of the world over the next few decades. The changes have strong economic implications, and many of them have already begun taking place.

One of the major projections is India's emergence as the world's most populous country in another fifteen years. India's population is expected to equal China's by 2028 and subsequently overtake it.

But while in 2028 both countries are expected to have a population of 1.45 billion each, India's population is projected to reach 1.5 billion in 2100 compared with China's 1.1 billion. The difference in the projection for the two countries' populations at the end of the century is because of the difference in the nature of their growth. India's population will continue to grow at a positive rate for several decades before declining in the later part of this century. But the rate of growth in China's population will become negative after 2030 and its population will start declining much before India's.

While the Indian population is expected to become more than China's by 2030, Nigeria is expected to overtake China as the second most populous country by the end of the century. Nigeria's current population is 173 million. Its population growth will be almost explosive as it is projected to surpass the US' population by the middle of the century and match China's by the end.

In fact, the African continent is projected to be the largest contributor to the increase in global population this century. Apart from Nigeria, other African countries projected to have rapid population growths are Tanzania, Congo, Ethiopia, Uganda and Niger. These countries will join Pakistan and Indonesia as the world's most populous countries following India and China.

These demographic changes have far-reaching economic implications. It is clear that some countries from Asia and Africa will be the largest global population hubs in the future. But they may not become the most prosperous economies. This is particularly true for African countries. While a resource-rich and relatively industrial African economy like Nigeria may grow and develop to become a major regional economy, other African economies experiencing high population growth, particularly the sub-Saharan economies, may remain economically backward. Even Nigeria, despite its economic potential, could find it difficult to expand its economy to a size that can generate enough livelihoods for its fast-growing population.

The problem of the demographic phenomenon of rapid population growth in high-fertility countries not being accompanied by the economic phenomenon of sustained high growth for creating jobs and generating employment is not a concern only for Africa. It also applies to populous Asian economies like India, Indonesia and Pakistan. The new population projections, while confirming the possibility of these countries enjoying demographic dividends over the next few decades, also draw attention to the economic imbalances that these demographic changes could produce.