This number represents the percentage increase in stand volume at age 6 years that would be expected from planting a specific family or mix of families or full-sib family or clone. For example, P32 would be a family that should produce 32% more wood volume at age 6 years compared to the local unimproved loblolly pine seedlings. The main benefit to landowners from the Productivity rating is the relative values for different families; a P38 is better than a P29 that is better than a P15; the higher the number, the more valuable the family. The actual growth and volume of the different families will depend on the site where it is planted and the silvicultural system used to manage the timber.