When the results came in, they revealed an enormous performance gap. The best outperformed the worst by a 10:1 ratio. The top programmers were also about 2.5 times better than the median. When DeMarco and Lister tried to figure out what accounted for this astonishing range, the factors that you’d think would matter—such as years of experience, salary, even the time spent completing the work—had little correlation to outcome. Programmers with ten years’ experience did no better than those with two years. The
Source: Maker vs. Manager: How Your Schedule Can Make or Break You