The R&D-abnormal return anomaly: a transaction cost explanation

Previous research finds a positive and significant relation between current increases in R&D expenditures and future abnormal stock returns. While the existence of this anomalous pattern is well-established, its underlying causes are the subject of much debate. Recent research also shows that transaction costs can lead to apparent market anomalies such as the post-earnings-announcement drift. We combine these two lines of research and posit that the positive relation between R&D increases and future abnormal stock returns is due to transaction costs. Consistent with this hypothesis, we find that abnormal returns on R&D-based, zero-net-investment portfolios disappear after incorporating standard measures of transaction costs. Overall, our results show that the R&D-abnormal return anomaly is more likely due to transaction costs than to the alternative hypotheses of market inefficiency or omitted risk factors.