Mean kinship is a measure of an individual’s relatedness to the whole population; the average inbreeding coefficient of the individual if paired to all other individuals of the breed at the same time. Selecting for lower MK individuals helps in keeping low population COI. In this way, mean kinship is a measure of value for genetic diversity-centric breeding.
The average MK of two individuals is the approximate MK of their offspring together, which is useful to know when only data of the parents is available. MK is a dynamic value, and will change slightly every time any dog produces offspring in the population.
Generally speaking high mean kinship means the individual has an over-represented or “common” pedigree, and low mean kinship means under-represented or “rare” pedigree. However, mean kinship is strictly a value for the full pedigree, not for the individual. An individual coming from an outside population (for example through a breed or variety cross) can have hundreds of names in their pedigree that are not present in the breed yet, resulting in low MK even after gross overcontribution from the individual.
Generally low MK individuals should breed more than high MK individuals, but no individual should breed past acceptable limits.
Pairing individuals with very different mean kinship values should be avoided, even if COI or MK were desirably low. When pairing a common pedigree with a rare pedigree, it will become impossible to increase the proportion of the valuable pedigree in the population without increasing the spread of the overrepresented pedigree at the same time.
For long-term benefit it is usually better to select breeding pairs from individuals with MK values closer to each other than at the extreme ends of the population, and let change happen more gradually. A possible good limit could be half of the current median mean kinship in the breed.