Yes. In fact, the link between satisfied workers and richer companies might be unique to nations like the United States. A new paper by Edmans and two professors from Warwick Business School finds that, in economies with flexible labor markets like the U.S. and the UK, "employee satisfaction is associated with positive abnormal [stock] returns." But in countries like Germany, where rules for hiring and firing are strict, the relationship between happy workers and thriving companies disappeared. In fact, spending too much on employee benefits appeared to be bad for growth.

Does this make any sense? It does if you think about incentives. Under the efficiency wage theory, employees see a happy work environment as a “gift” from the firm, which is reciprocated with a “gift” of greater effort. Studies going back to the 1960s have found that satisfied workers are more likely to work harder because they develop an emotional connection with the office. In America, to drink the free Coconut Water is to drink the corporate Kool Aid.

In countries like Germany with more tightly regulated labor markets, however, "legislation already provides minimum standards for worker welfare and so additional expenditure may exhibit diminishing returns," the researchers write. When there's no chance of us leaving, why waste the energy to seduce us.

If the Happy Worker Premium is real, should funds treat the “100 Best Companies to Work For in America” as a target list? Older investors might feel a certain sub-Google enthusiasm for serving analysts free seared salmon lunches, but they might be underestimating job satisfaction as a long-term signal of a company's stock growth. As some clever conservative economists have said, if liberals are so sure that higher wages are good for companies—particularly in ways that are not immediately obvious to other investors—then they should heavily invest in high-wage companies, since those firms are theoretically undervalued by the market. An investment group that adopted the Happy Worker Theory might not find it universally applicable—after all, it appears to have no effect in Germany and other countries with tight labor markets—but for tech firms with a large domestic footprint, it might be an investment idea worth exploring.

To close, there are a few reasons to be skeptical about the power of perks. First, these papers don't prove that happy workers are solely and directly responsible for raising the valuation of their companies. You could just as easily say that gifted managers (a) understand how to retain talent and (b) understand how to grow the company. Or you could argue that many talented workers who are generally indifferent to perks are still more likely to get a job at highly desired companies. Free ice cream truck or no, they'll be happy doing a job where they shine.