Why We Have to Go Back to a 40-Hour Work Week to Keep Our Sanity
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Another is that overtime is only effective over very short sprints. This is because (as Sidney Chapman showed in 1909) daily productivity starts falling off in the second week, and declines rapidly with every successive week as burnout sets in. Without adequate rest, recreation, nutrition, and time off to just be, people get dull and stupid. They can't focus. They spend more time answering e-mail and goofing off than they do working. They make mistakes that they'd never make if they were rested; and fixing those mistakes takes longer because they're fried. Robinson writes that he’s seen overworked software teams descend into a negative-progress mode, where they are actually losing ground week over week because they're so mentally exhausted that they're making more errors than they can fix.
The Business Roundtable study found that after just eight 60-hour weeks, the fall-off in productivity is so marked that the average team would have actually gotten just as much done and been better off if they’d just stuck to a 40-hour week all along. And at 70- or 80-hour weeks, the fall-off happens even faster: at 80 hours, the break-even point is reached in just three weeks.
And finally: these death marches take a longer-term productivity toll as well. Once the crisis has passed and that 60-hour-a-week team gets to go back to its regular 40, it can take several more weeks before the burnout begins to lift enough for them to resume their typical productivity level. So, for a while, you’ll get significantly less than a full 40 out of them.
Wise managers who understand this will a) avoid requiring overtime crunches, because they're acutely aware of the serious longer-term productivity hit that inevitably follows; b) keep the crunches as short as possible when they are necessary; and c) give their teams a few days off -- one to two comp days per overtime week worked is about right -- at the end of a hard sprint. This downtime enables them recuperate more quickly and completely. It's much more productive to have them gone for the next week — and then back on the job, rested and ready to work — than have them at their workstations but too fried to get anything useful done for the next month.
So, to summarize: Adding more hours to the workday does not correlate one-to-one with higher productivity. Working overtime is unsustainable in anything but the very short term. And working a lot of overtime creates a level of burnout that sets in far sooner, is far more acute, and requires much more to fix than most bosses or workers think it does. The research proves that anything more than a very few weeks of this does more harm than good.
Enter the Knowledge Worker
After WWII, as the GI Bill sent more workers into white-collar jobs, employers at first assumed that the limits that applied to industrial workers probably didn’t apply to knowledge workers. Everybody knew that eight hours a day was pretty much the limit for a guy swinging a hammer or a shovel; but those grey-flannel guys are just sitting at desks. We’re paying them more; shouldn’t we be able to ask more of them?
The short answer is: no. In fact, research shows that knowledge workers actually have fewer good hours in a day than manual laborers do — on average, about six hours, as opposed to eight. It sounds strange, but if you’re a knowledge worker, the truth of this may become clear if you think about your own typical work day. Odds are good that you probably turn out five or six good, productive hours of hard mental work; and then spend the other two or three hours on the job in meetings, answering e-mail, making phone calls, and so on. You can stay longer if your boss asks; but after six hours, all he's really got left is a butt in a chair. Your brain has already clocked out and gone home.