[AdmSmith]

There are several studies on this, one is in Public Policy & Aging Report by Mark L. Haas:

For example, Russia’s working-age population (ages 15 to 64) is expected to shrink 34 percent by 2050. The country’s population is already decreasing by 700,000 people per year. Also by 2050, China’s median age is predicted to be nearly 45. Given this fact, Haas believes their government will be faced with a difficult choice: allow growing levels of poverty within an exploding elderly population, or provide the resources necessary to combat this problem by diverting funds from military spending.

The United States is not immune to the problems of global aging, but it does stand to fare better than many of its rivals. In 2050, this country’s median age will be the lowest of any of the great powers. And by the same year, the working-age population in the U.S. is expected to increase by 31 percent. Additionally, the United States has a relatively well-funded pension system.
http://www.scienceagogo.com/news/20080024194254data_trunc_sys.shtml

Drunken Nation: Russia’s Depopulation Bomb

Nicholas Eberstadt
http://www.worldaffairsjournal.org/2009%20-%20Spring/full-Eberstadt.html

Spengler, aka David P Goldman, wrote an analysis http://www.atimes.com/atimes/Central_Asia/JH19Ag04.html

[SunkenCiv]

Whoops! Thanks AdmSmith.