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α: calibrated so average coauthorship-adjusted count equals average raw count
Over the last two decades, millet prices in Niger have experienced several periods of spectacular increases during which they seemed to go well above their fundamental value. The presence of rational speculative bubbles might explain these episodes of price booms followed by rapid reversals. Relying on the present value model of commodity pricing we test for the presence of periodically and partially collapsing price bubbles for 31 millet markets in Niger by using right-tailed recursive unit root tests. Once controlled for observed fundamentals, one-third of price series manifest explosive behaviour akin to a bubble. Under the rational bubble hypothesis, the results indicate that the traders operating in separate geographic areas differ with respect to information quality. A competing interpretation is that some large traders use their market power to charge higher prices to consumers.