Real Campaign "drop-offs"
What are the "drop offs" from ads purchased, to ads served, to ads rendered.
Updated 5/24/2021 with another example (33% drop off from bids won to ads served)
From the number of bids won, to the number of ads served, to the number of ads rendered and measured.
In my own experimental campaign, I purchased 1 million ad impressions, my ad server recorded 931k ads served; and my FouAnalytics tag measured 746k ad impressions that finished rendering, so our tag could be fired. The discrepancy of about 25% is the difference between what you paid for (number of bids won) and the number of ads that were served and rendered in browser.
DSP tells you how many bids you won (1 million ad impressions purchased)
my ad server (Revive) tells me how many ads were called and sent out from ad server (931k)
my measurement tag fires after the ad finishes rendering (746k rendered ads) - which is an approximate 25% drop-off from the 1 million ad impressions I paid for.