The second version of equity market timing involves irrational investors(or managers) and time-varying mispricing (or perceptions of mispricing).Managers issue equity when they believe its cost is irrationally low andrepurchase equity when they believe its cost is irrationally high. Market-to-book is well known to be inversely related to future equity returns, andextreme values of market-to-book have been connected to extreme investorexpectations by La Porta (1996), La Porta et al. (1997), Frankel and Lee(1998), and Shleifer (2000). If managers are trying to exploit too-extremeexpectations, net equity issues will be positively related to market-to-book,which is the case empirically. If there is no optimal capital structure, managersneed not reverse these decisions when the firm appears to be correctlyvalued and the cost of equity appears to be normal, leaving temporary fluctuationsin market-to-book to have permanent effects on leverage.It is important to keep in mind that this second version of market timingdoes not require that the market actually be inefficient. It does not askmanagers to successfully predict stock returns. The critical assumption issimply that managers believe that they can time the market.Our results do not discriminate between these two versions of market timing.Elements of each are present in the financing model of Stein (1996). Inthe survey by Graham and Harvey (2001), CFOs admit to trying to time theequity market, and two-thirds of those that have considered issuing commonstock report that "the amount by which our stock is undervalued or overvalued"was an important consideration. This survey evidence supports thecritical assumption in the market timing theory mentioned above-which isthat managers believe they can time the market-but does not immediatelydistinguish between the mispricing and the dynamic asymmetric informationversion of market timing.The evidence that distinctly supports the mispricing version comes fromthe low long-run stock returns following equity issues and the high long-runreturns following repurchases. The magnitudes of these effects suggest thatmanagers are, on average, successful at equity market timing. For example,Loughran and Ritter (1995) point out that the long-run abnormal returns toequity issuers, a rough measure of the magnitude of exploitable mispricing,are an order of magnitude bigger than the announcement effects of equityissues, a rough measure of the recognition of asymmetric information. Theevidence in Baker and Wurgler (2000) suggests that equity issuers can, onaverage, also time the market component of the cost of equity. This makesthe total gains to market timing even bigger in comparison to the adverseannouncement effect, and suggests that outright mispricing is the primarymotivation for equity market timing.In summary, a range of evidence indicates that market timing is an importantaspect of real financing decisions. Our results appear to supportthis view. Other interpretations cannot be completely ruled out, but we believethat the results are most naturally explained by the theory that leveragearises as the cumulative outcome of attempts to time the equity market.