In 1913 Maximilian Ringelmann, a French engineer, studied the performance of horses. He concluded that the power of two animals pulling a coach did not equal twice the power of a single horse. Surprised by this result, he extended his research to humans. He had several men pull a rope and measured the force applied by each individual. On average, if two people were pulling together, each invested just 93% of their individual strength, when three pulled together, it was 85%, and with eight people, just 49%.
Excerpt from: The Art of Thinking Clearly by Rolf Dobelli