This is a monster of a report (200 pages plus – 12 Mb) called An Aging World: 2008 from the U.S. Department of Commerce.
Definitely a reference guide you should download to your online library.
The above chart shows how Japan is leading the way as the world’s oldest country.
Original Post: http://www.20plus30.com/blog/2009/08/httpwwwcensusgovprod2009pubsp95-09-1pdf.html