Many systems require slack in order to run smoothly. Old reel-to-reel tape recorders needed an extra bit of tape fed into the mechanism to ensure that it wouldn’t rip. Your coffee grinder won’t grind if you overstuff it. And consider roadways: In principle, if a road is 85 percent full and everybody goes at the same speed, all cars can easily fit with some room between them. But if one driver speeds up just a bit and then needs to brake, everyone behind that car has to brake as well. Thus, at 85 percent there is enough road but not enough slack to absorb small shocks, and traffic grinds to a halt.
Why excess capacity leads to greater efficiency.
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