Croci, Petmezas and Vagenas-Nanos (2010) showed that in UK acquisitions 1990–2005 the interaction between aggregate stock-market valuation and managerial overconfidence shapes bidder gains: non-overconfident managers earn their largest announcement returns in high-valuation markets, overconfident managers earn weak announcement returns and large 36-month losses, and market valuation predicts short-run but not long-run abnormal returns. The paper explicitly leaves unresolved whether contractual compensation devices and corporate governance arrangements can actually prevent overconfident managers from undertaking value-destroying acquisitions, whether its findings are robust to the data-driven sample restriction imposed by the option-based overconfidence proxy, and why valuation-driven short-run premiums do not persist long-run. All three threads remain open: US evidence that strong boards mitigate overconfident CEOs' acquisition mistakes exists (Kolasinski and Li 2013) but no causal, UK, or compensation-device test; out-of-sample evidence on the valuation thread conflicts (Farinos, Herrero and Latorre 2020); and theory complicates the mitigation premise by showing overconfident CEOs can be rationally selected under value-maximizing governance (Goel and Thakor 2008).

Background

Two behavioral theories explain why acquiring firms' shareholders often gain little from mergers and acquisitions (M&A). Roll's (1986) hubris hypothesis holds that markets are efficient but managers are not: overconfident managers systematically overestimate the synergies a takeover will create and therefore overpay, destroying their own shareholders' wealth. Shleifer and Vishny's (2003) market valuation theory instead holds that managers are rational but markets are not: rational managers exploit periods of overvalued stock to buy less-overvalued targets, so deals announced in high-valuation ('hot') markets should look different from deals announced when markets are depressed. A bidder's stock-market gain around a deal is measured by the cumulative abnormal return (CAR), the sum of differences between the bidder's realized return and a benchmark return over an event window around the announcement (an 'event study'); long-run performance is measured by the buy-and-hold abnormal return (BHAR), the compounded difference between the bidder's return and that of a size- and book-to-market-matched control firm over months after the deal, or by calendar-time abnormal returns (CTAR), the average return of a portfolio that continuously holds recent acquirers. Managerial overconfidence is commonly measured by option-exercise behavior, following Malmendier and Tate (2008): because risk-averse executives should rationally exercise vested stock options well before expiry, a manager who holds options until the final year before expiration is classified as overconfident. An alternative proxy defines as overconfident any manager who completes five or more acquisitions within three years, a pattern attributed to self-attribution bias (the tendency to attribute success to one's own skill and failure to bad luck, which reinforces overconfidence after early deal successes; Doukas and Petmezas 2007). Croci, Petmezas and Vagenas-Nanos (2010) combined the two theories in a sample of UK acquisitions (1990–2005): starting from 3,223 deals by London Stock Exchange bidders, option data allowed classifying managers in only 848 deals, and months were sorted into high, neutral, and low valuation periods using the detrended price-to-earnings (P/E) ratio of the FT-All Share index (each month's P/E minus the best-fit straight line estimated by ordinary least squares over that month and the five preceding years, with detrended months then grouped relative to their past five-year average). They found that non-overconfident bidders earn positive five-day announcement CARs in all valuation periods (largest mean 1.36% in high-valuation periods), overconfident bidders earn an insignificant 0.16% on average, the differential between the two extreme portfolios (non-overconfident/high-valuation versus overconfident/low-valuation) is 3.05%, and results are robust to the multiple-acquirer proxy and to controls for deal and firm characteristics. Over 36 months, overconfident bidders' BHAR is a significant −21.75% versus an insignificant +2.98% for non-overconfident bidders, but valuation period has no significant long-run effect. From these findings the paper draws implications and acknowledges gaps that define the present problem: the option-based proxy forces the main sample to a 26% subsample of all deals ('we cannot draw strong inferences from the number of acquisitions in high valuation periods'); compensation contracts tied to firm performance may not stop biased managers ('it is still uncertain whether they will cancel their value-destroying corporate actions'), pointing to board independence as the remaining safeguard; and the short-run valuation effect's disappearance in the long run lacks an explanation. For context, US evidence (Bouwman, Fuller and Nain 2009) had found that hot-market acquisitions earn better announcement returns but worse long-run returns, so the UK long-run neutrality of valuation is itself a stylized fact needing reconciliation; the field's synthesis (Malmendier and Tate 2015) treats overconfidence measurement and its governance implications as an ongoing research frontier.

Problem Statement

Building on the UK evidence of Croci, Petmezas and Vagenas-Nanos (2010) that managerial overconfidence interacts with market valuation in shaping bidder gains, three interlinked questions remain open, jointly serving one objective — establishing under what institutional and market conditions managerial overconfidence destroys acquisition value: (1) Mitigation: do contractual compensation devices (stock options, stock grants tied to firm performance) and corporate governance arrangements (board independence, board strength) actually prevent overconfident managers from undertaking value-destroying acquisitions, or are overconfident managers instead selected and retained under value-maximizing governance so that these devices cannot serve as correctives? Existing affirmative evidence is US-only, board-focused (Kolasinski and Li 2013), and not causally identified, which leaves open whether contractual compensation devices and governance arrangements discipline overconfident acquirers in the UK, and whether any observed effect reflects discipline rather than selection. (2) Persistence and mechanism: why do market-valuation-driven announcement-window CAR gains (largest for non-overconfident bidders in high-valuation periods) fail to translate into systematic long-run abnormal returns (36-month BHAR/CTAR), when US evidence (Bouwman, Fuller and Nain 2009) shows hot-market deals underperforming long run and Spanish evidence contradicts both? The UK long-run neutrality of valuation, and its divergence from the US and Spanish evidence, remains to be explained. (3) Measurement and sample validity: is the overconfidence-valuation interaction robust when the overconfidence proxy no longer restricts the sample — i.e., does it survive on classification-free or proxy-independent samples (the option-exercise proxy covers only 848 of 3,223 UK deals, and the paper's own multiple-acquirer robustness check rests on a different construct), so that the documented value destruction is not proxy- or selection-driven? The three questions jointly serve the single objective, and none is independently resolving.

References

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