When opinion leaders and policymakers talk about world population growth, they generally rely upon the “medium variant” projection issued by the UN’s Population Division.  In the UN’s 2006 Revision the “medium variant” shows global population growth rising to 9.2 billion by 2050.  That projection assumes however, that total fertility in all countries will converge eventually toward a level of 1.85 children per woman, though many countries will not reach that level by 2050. 

If fertility rates do not fall as fast as projected by the UN’s medium variant, world population (currently 6.7 billion) could exceed the projected 9.2 billion mark for 2050.  Earlier this month, the Census Bureau released the latest revision of its International Data Base (IDB).  Based on updated projections for 34 nations, the latest Census Bureau projection shows global population rising to 9.5 billion by 2050. 

The difference between the UN and Census Bureau’s projection for 2050 (9.2 billion vs. 9.5 billion) may not seem that large, but it’s important to remember that population growth has momentum.  Virtually everyone agrees that global population will, at some point in the 21st Century, stabilize and begin to decline.  But, when?  And at what level?

The latest Census Bureau report indicates that the rate of global population growth, currently about 1.2 percent per year, will decline in the next 42 years. Global population, however, will still be increasing by 0.5 percent a year by 2050.  That means that world population, currently growing by about 79 million people a year, would still be growing by close to 50 million people a year in 2050.

The Census Bureau's latest global population projection received virtually no coverage in the press.  But, as the debate grows about the role that population growth plays in climate change, the food crisis, and resource depletion, you can expect more attention will be paid to these projections—and their underlying assumptions.  Stay tuned.