In Kimura’s original calculations, mutations with |2 N"s"|<1 or |"s"|≤1/(2N) are defined as neutral. In this equation, N is the effective population size and is a quantitative measurement of the ideal population size that assumes such constants as equal sex ratios and no emigration, migration, mutation nor selection. Conservatively, it is often assumed that effective population size is approximately one fifth of the total population size. "s" is the selection coefficient and is a value between 0 and 1. It is a measurement of the contribution of a genotype to the next generation where a value of 1 would be completely selected against and make no contribution and 0 is not selected against at all. This definition of neutral mutation has been criticized due to the fact that very large effective population sizes can make mutations with small selection coefficients appear non neutral. Additionally, mutations with high selection coefficients can appear neutral in very small populations. The testable hypothesis of Kimura and others showed that polymorphism within species are approximately that which would be expected in a neutral evolutionary model.