What change in demographics was observed in developed countries in the twenty-first century?

Population is undeniably important-but how, for whom, and with what consequences is a complex story. Two things are certain:

Population issues in the 21st century are different from those in the last century.

With the development world midway through an uncertain effort to reach the Millennium Development Goals by 2015, population issues will be central to the success or failure of six of the eight goals.