A key theoretical prediction in financial economics is that under risk neutrality and rational expectations a currency’s forward rates should form unbiased predictors of future spot rates. Yet scores of empirical studies report negative slope coefficients from regressions of spot rates on forward rates. We collect 3643 estimates from 91 research articles and using recently developed techniques investigate the effect of publication and misspecification biases on the reported results. Correcting for these biases yields slope coefficients in the intervals (0.23,0.45) and (0.95,1.16) for the currencies of developed and emerging countries respectively, which implies that empirical evidence is in line with the theoretical prediction for emerging economies and less puzzling than commonly thought for developed economies. Our results also suggest that the coefficients are systematically influenced by the choice of data, numeraire currency, and estimation method.

金融经济学中一项重要的理论预测是，在风险中性和理性预期的情况下，货币的远期汇率应构成未来即期汇率的无偏预测因素。然而，许多实证研究报告了即期汇率对远期汇率的回归所产生的负斜率系数。我们从91篇研究文章中收集了3643项估算值，并使用最新开发的技术调查了发表结果和错误指定偏见对报告结果的影响。校正这些偏差后，发达国家和新兴国家的货币的斜率系数分别为（0.23,0.45）和（0.95,1.16），这表明经验证据与新兴经济体的理论预测相符，令人困惑的是通常被认为是发达经济体。