Average Lead Time calculation

What is the calculation for Average Lead Time in the Item Branch file?

My understanding is that this is a weighted calculation. So if you have a large number of units on one purchase order line, that has a bigger impact on the avererage lead time than other receipts would. Lead time is supposed to be calculated as Receipt Date - Purchase Order Date. Take that number of days times the units (F43121). Sum up that result, and divide that by the total units received to find the average lead time. For example, say you had 10 units received in 10 days. 10 * 10 = 100. Next you had 100 units received in 20 days. 100 * 20 = 2000. 100 + 2000 = 2100. 2100 / 110 = 19.09 days average lead time. This should be getting updated in the receipts program. This is my understanding of how this is supposed to work. You would think at some point you might want to have the ability to reset this somehow, otherwise your older history may be impacting what your more real current lead time might be, but I don't know if there is a way to do that.
John Dickey

Thanks. I couldn't find any JDE documentation on this and trying to read the program code to figure it out was like reading greek (and I'm a programmer!). I do believe there is a regen program (P43900) to reset the value, but it reads the PO receipts file (F43121) so it would recalc based on the volume of history that is kept therefore your point is still very valid about the impact of older history.