Coupe probably felt he had reason to celebrate: Sainsbury’s stock jumped 20% April 30 after it announced plans to merge with Walmart’s Asda unit. Coupe, who owned over a million Sainsbury shares as of last year, saw his own wealth climb an estimated $606,000 as a result of the news, CNN Money reported.

Grocery unions, who fear the merger will mean job cuts, were not charmed by Coupe’s singing, and the CEO apologized for his “unguarded moment,” saying the song was on his mind because he saw it performed in the musical 42nd Street last year.

CEOs celebrating soaring share prices is nothing new, of course. About a decade ago, when I covered the casino industry, I met with Las Vegas Sands CEO Sheldon Adelson in his board room in The Venetian. The company’s shares were on a tear (the next week, Forbes would name Adelson the world’s third-richest person) and the mood in the office was bouyant. As executives wandered through, they would pass along the latest share price to their boss, who would let out an exultant yip.

It’s only natural that CEOs would pay attention to share prices: They are, after all, immediate feedback from investors about the health of their companies. Yet share prices are also shaped by a great many other forces—from geo-political concerns to the stumbles of a rival—that may only tangentially impact the company. And focusing on the day-to-day (or minute-to-minute) fluctuations of shares can distract executives from building healthy companies over the long term.

CEOs who obsess over share prices risk falling victim to what psychologists describe as the “availability heuristic,” a mental shortcut where we place greater weight on information that’s more recent or memorable, even if it is less significant. The heuristic is why people overrate the odds of dying in a terrorist attack vs. a more mundane demise.

Companies run by CEOs guided by short-term thinking are less profitable than ones built for the long term, according to research from McKinsey Global Institute, and making decisions based on their impact on share price can lead to deceptive practices. Better to take the attitude of Tesla CEO Elon Musk, who last year broke the rule about not commenting on stock prices. He admitted his shares were overpriced.

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