Periodic annual increment

[1] For sigmoid growth, the graph of PAI increases rapidly and then quickly declines, approaching zero.

PAI may go negative if a tree loses volume due to damage or disease.

Growth per cent indicates the rate of increase with relation to the wood capital required for its production, this is usually based on a single year's growth.

Example: Say that the growth period is from age 5 to age 10, and the yield (height of the tree), is 14 feet at the beginning of the period and 34 feet at the end.

When mean annual increment (MAI) and periodic annual increment (PAI) are graphed together, the point in which they intersect is called the biological rotation age.