According to the United Nations’ population projections, life expectancy in the world’s poorest developing countries will increase to 69 years in the next four decades if progress in battling HIV/AIDS and other infectious diseases continues, The Montréal Gazette reports. The report attributes the jump in life expectancy to successful reduction in child mortality in poor countries.

In developing countries whose economies were advancing before the economic crisis, life expectancy will rise from 67 to 75 in four decades. With the extension of life spans, however, officials fear that job rivalry will arise between young and old populations.

Unlike in rich countries, the people of the developing world do not have access to government or private pensions, and saving for the future is difficult because of lower pay. That means older people are forced to work as long as possible.

On average, people live to be 83 in the wealthiest countries today, the report says.