Column A has time series data from A20 to A1850
Column B has a formula calculating the smoothed percentage change in the Col A data.
The formula is entered in B1400, copied, and pasted from B1401 to end.
The calculated answers appear from B1400 to B1602 but not from B1603 to end.
The formulas are correct from B1400 to end.

Q: Why does the answer stop appearing after a number of sequential calculations down Col B?

Good question. Let's see the workbook.

If you don't want to post it, then try using the Formula Evaluation toolbar to analyze what's going on in those cells.

In the last cell it works, click on Formula Evaluator and "step through" the formula watching it unfold until you see the final result.

Now repeat that on the first cell where it stopped working. You should see the exact moment in the formula where it doesn't do what you expect. That should give you a clue as to the error in the formula logic.

Thanks, Jim - you pointed me towards answering the question.
Nat