Rank Selection is similar to fitness-proportionate selection except that selection probability is proportional to relative fitness rather than absolute fitness. In other words, it doesn't make any difference whether the fittest candidate is ten times fitter than the next fittest or 0.001% fitter. In both cases the selection probabilities would be the same; all that matters is the ranking relative to other individuals.

Rank selection will tend to avoid premature convergence by tempering selection pressure for large fitness differentials that occur in early generations. Conversely, by amplifying small fitness differences in later generations, selection pressure is increased compared to alternative selection strategies.