Inflation-adjusted interest rates are still too low in developing nations for Citigroup Inc. and Goldman Sachs Group Inc. to foresee an end to the worst emerging-market currency selloff in five years.

One-year borrowing costs in Turkey are 3.6 percent, less than half of the average in the three years before the 2008 global financial crisis, even after the central bank doubled its benchmark rate last week, according to data compiled by Bloomberg. The real yield for Mexico is almost zero, while South Africa's is 1.4 percent, compared with an average of 2 percent over the past decade.

Central-bank rate increases in Turkey, India, and South Africa last week failed to contain January's 3 percent selloff in emerging-market currencies. Citigroup says yields aren't high enough to attract the capital needed to finance current-account deficits in some of those nations. Competition for capital is intensifying, with the Federal Reserve paring monetary stimulus, while the International Monetary Fund is calling for “urgent policy action.”