While "it is true that real prices have fallen for a large number of commodities in the course of the 20th century" this has not been a continuous trend, certainly not for all commodities and it has proved difficult to forecast the relationships between manufacturing and primary good-producing nations regarding commodities and trade, given the considerable variance exhibited by recent history (Newbald et al. 2005, p. 493). Nor have all nations that have taken the advice to shift from commodities to manufacturing prospered. One "study observed rapidly rising shares of manufactured and electronic goods in Korea's total exports and a trend decline in Korea's terms of trade" from 1967 -- 2001, but "contrary to the expectation of Prebisch, the increasing proportion of manufactured and electronic goods in Korea's exports exerted no favorable influence on the course of Korea's terms of trade. In fact, this study supports the later extension to the Prebisch -- Singer hypothesis, that rather than an emphasis on relations between types of commodities there should be an emphasis on relations between types of countries," stressing that inequities between core and peripheral nations persist, regardless of what goods are the objects of trade (Sarkar 2005).

The theory's harshest critics have stated that it encouraged many nations to embark upon an industrially-driven economy that it was ill-prepared for, and did not fundamentally address the real, often political reasons that there are inequities between the developing and the developed...

Looking around the globe it is easy to see both confirmations and challenges to the thesis -- formerly agriculturally-driven China and India are prospering, for example, but many nations in the developing world with abundant natural resources import their food because of poor farming practices that have been disrupted by political turmoil that cannot be explained purely in terms of the developed world's manufacturing power.
Works Cited

Cuddington, John T., Rodney Ludema, and Shamila A. Jayasuriya. "Prebisch-Singer redux."

Georgetown University. January 2002 draft. May 4, 2009.

http://www.bcentral.cl/conferencias-seminarios/otras-conferencias/pdf/2002recursosnaturales/cuddludjaya.pdf

Newbold, Paul N., Stephan Pfaffenzeller, & Anthony Rayner. "How well are long-run commodity price series characterized by trend components?" Journal of International Development 17. 4 (May 1, 2005): 479-494. http://www.proquest.com / (accessed May 4, 2009)

"Prebisch-Singer theory." Everything2.com. 2005. May 4, 2009.

http://everything2.com/title/Prebisch-Singer%2520thesis

"Latin America's Keynes." The Economist. March 5, 2009. May 4, 2009.

http://www.economist.com/books/displaystory.cfm?story_id=13226316

Sarkar, Prabirjit. "Rising manufacture exports and terms of trade: the case study of Korea."

Progress in Development Studies. 5. 2 (April 1, 2005): 83-88. http://www.proquest.com / (accessed May 4, 2009).