By default, breeding values are centered on zero (with negative and positive values). This is based on the assumptions that all base (ancestral) individuals are equal and they mated at random to produce the population under study. This is not a safe assumption when the population comprises a mixture of different genetic groups. If the group effect is ignored, additive genetic variance estimates can be biased upward, and selection may favor a particular provenance at the risk of introducing some inbreeding in future generations. The provenance or founder effect should be accounted for when estimating breeding values to avoid such problems.