Population size is an important choice in the construction of a genetic algorithm.
This choice has not been addressed analytically for GAs whose chromosomes are permutations. This paper describes a simple estimate of appropriate population size in a GA for TSP whose crossover operator builds offspring tours using edges from parent tours. The estimate sets the population size large enough that the initial population is likely to include every edge in a shortest tour of the problem instance's cities. In runs on several well-known instances of TSP, the algorithm's performance deteriorates with populations significantly smaller or larger than the estimate recommends.