Sire Reference Schemes were established to overcome the problem of comparing the breeding potential of two rams reared in different flocks. These schemes encourage recording breeders to work together to share popular breeding lines in order to create genetic linkage between recording flocks. The progeny of these ‘reference sires’ create a benchmark against which all other lambs can be compared, enabling them to be ranked as if they were in a single flock. By linking the flocks in this way the size of the population from which replacements could be selected is greatly enlarged. This co-operative approach has enabled recording breeders to make much faster rates of breeding improvement, choosing the very best sires from thousands of potential candidates.