Sow performance can be evaluated many different ways, but some of the key performance indicators are farrowing rate, total born and total born alive, pigs weaned per sow, piglet survivability, and pigs weaned per mated female per year. Using the % of litters under 7 and above 12 are relatively new key performance indicators, and are useful for highlighting when a lot of litter variability is occurring. Litter size and litter variability often impact overall sow performance, and it is not always clear what is causing the variability. Having consistently large litter sizes will increase production, reduce work per sow (such as for fostering), and increased udder capacity in gilts. As well, more pigs weaned reduces the cost of lactation feed per pig.