(See the first part of this article here for background.)
How, exactly, does AMS assign the lagged sales data?
I've established, via occasional spot checks during my tests in the previous article, that it takes several days for the Orders (Units Sold) data to finalize for the AMS-reported sales.
I was asked if it trickles in randomly, or if it is assigned to the particular days that it should have been applied to originally. Since I didn't know the answer, I decided to find out.
I also now had a corrective for my “organic sales = effectively zero” assumption. 3 weeks of testing in August established a baseline for my 2 advertised products (1st book in series for 2 series (ANNWN-N1 and CHAIN-N1) of 0.2 units per title per day.
So, I used the July 1-July 29 test period (which is now over a month old) and took a look.
First, I used the AMS reports to do a day by day look at the reported units sold. I compared that with my spot check during the month of sales as-of a particular date — that ran out well past the end of the month to let the lagging data catch up.
I discovered that the lagged data is assigned after the fact to particular days, presumably the dates that would have been correct at the time. In other words, my spot checks of units sold as of date X for the month are smaller than they would be if I could do that now, because lagging data has been applied to those dates sometime between when I did the spot check and now, a month later.
Undercounting & Missing data
So, now that the data is final, what does the undercounting look like?