The widespread notion that dollar-cost averaging can help an investor minimize the risk of investing all of one's capital in the market at an inappropriate time is aptly stated by Malkiel [4, p. 242]:Periodic investments of equal dollar amounts in common stocks can substantially reduce (but not avoid) the risks of equity investment by insuring that the entire portfolio of stocks will not be purchased at temporarily inflated prices. The investor who makes equal dollar investments will buy fewer shares when prices are high and more shares when prices are low.

Earlier research finds correlation between sentiment and future economic growth, but disagrees on the channel that explains this result. We shed new light on this issue by exploiting cross-sectional variation in country size and market efficiency. We find that sentiment shocks in the largest advanced economies increase economic activity, but only temporarily and without affecting productivity. Conversely, sentiment shocks in smaller or less advanced economies predict prolonged economic growth and a corresponding increase in productivity. The results support the view that sentiment can create economic booms, although only in economies where sentiment and fundamentals are harder to disentangle.