Lay The Foundation(s) Of

http://www.nytimes.com/2011/04/14/world/middleeast/14iht-M14B-MAGHREB-INSURE.html

"But analysts say that advances in the past decade have laid the foundation for potentially high long-term growth of the sector in Algeria, Morocco and Tunisia. "

http://www.nytimes.com/2011/07/13/opinion/13likosky.html

"The World Bank, the Inter-American Development Bank, the Asian Development Bank and similar institutions helped debt-burdened developing countries to grow through infrastructure investments and laid the foundations for the global high-tech economy."

When should I use the singular "foundation" and when to use the plural "foundations"?