NOTE 18I: Hill (1982) gives the calculation of v), although with different notation. The agreeement between the two different approaches (one based on overall breeding value and the other based on fixation of individual alleles) depends on the assumption that alleles are equally likely to be positive as to be negative. Robertson (1960) gives a calculation that is based on fixation probabilities in a similar way, but assumes small N_es; this leads to the prediction 2N_eβV_m as in ii).