A big new study finds compelling evidence that happy workers are more productive

With more companies thinking about the impact of how they treat workers, it's useful to know that a large study of call-center workers in the UK affirms what we all suspected: Employees are indeed more productive when they're happier.

The research, led by the Saïd Business School at the University of Oxford, UK, collected data from around 1,800 call-center workers employed by British Telecom (BT), one of the UK's largest private employers, over a six-month period.

The employees were asked to fill out a simple survey each week, with emoji used to denote their level of happiness. The researchers then compared the happiness data to the measures used by BT to gauge productivity: call length, the percentage of calls converted into sales-for example of broadband or phone contracts-and the extent to which employees adhered to a work schedule. Alongside these measures, the researchers tracked attendance, hours worked, breaks, and customer satisfaction.

The academics discovered that workers were on average 13% more productive in weeks when they self-reported as being very happy, compared to those weeks when people reported being very unhappy.

The paper, published by Saïd Business School, was also presented to a UK government working group studying the economics of wellbeing. Though a link between happiness and productivity has been much discussed, one of the study's authors, economist Jan-Emmanuel De Neve of Oxford University, said there "has never been such strong evidence" of a connection, and employers should take note. "While this [is] clearly in the interest of workers themselves, our analysis suggests it is also in the interests of their employers," he said in a press release.

But there may be little employers can do about a factor found to materially dampen workers' spirits: the rain.

Because the researchers wanted to measure the influence of an external force that, they predicted, might effect workers on more than an individual level, they included weather information in the study. They created a "Bad Weather Index" that included the incidence of rain, fog, and snow near the call centers. Poor weather had a strong effect on the happiness of the workers, which in turn affected their sales, the researchers discovered. (The workers were based at 11 different call centers around the UK, with a wide geographic spread between southwest England and northwest Scotland. Calls could come from anywhere in the country, though, ensuring that the measured weather effect wasn't making callers less likely to buy.)

Is it possible that working productively simply made workers happier, rather than their state of mind spurring higher sales? The researchers address the issue, noting that prior research suggests that, in routine work setting such as call-center jobs, the satisfaction gained from high achievement is slight compared with other factors, giving them confidence that the relationship between mind state and sales is indeed causal.

The research builds on previous work by some of the same authors that discovered-perhaps unsurprisingly-that workers are happier if they're paid better and are more secure. The current research, they note, doesn't explore what firms can actually do to make workers happier. Another recent US study might hold a clue, but its conclusion about what workers want most is not something call-center workers are likely to see anytime soon: unlimited paid time off.