India’s population is expected to surpass China’s in about seven years and Nigeria is projected to overtake the United States and become the third most populous country in the world shortly before 2050, a U.N. report said Wednesday.

The report by the Department of Economic and Social Affairs’ Population Division forecasts that the current world population of nearly 7.6 billion will increase to 8.6 billion by 2030, 9.8 billion in 2050 and 11.2 billion in 2100.

It said roughly 83 million people are added to the world’s population every year and the upward trend is expected to continue even with a continuing decline in fertility rates, which have fallen steadily since the 1960s.

India, currently second largest with 1.3 billion people, is expected to surpass China's 1.4 billion population within seven years.

While fertility levels are declining nearly everywhere, the 47 least-developed countries had high fertility rates averaging 4.3 births per woman between 2010 and 2015, driving their growth.

As a result, 26 countries in Africa are projected to at least double in size by 2050.  Nigeria, with the fastest growing population worldwide, will overtake the United States in size by then, the U.N. said.

The concentration of population growth in the poorest countries will make it difficult to ensure young people get enough food, health care, education, and other necessities, the U.N. said.

Meanwhile, populations in Europe, Japan, and other developed countries will continue aging and declining.

Countries where fertility rates are below replacement level include China, the United States, Brazil, Russia, Japan, Vietnam, Iran, Thailand, and Britain.

An influx of refugees and migrants will compensate for dwindling births, especially in Europe, but will not prevent overall population declines.