Sell-Through Rate STR (aka sold-out rate, inventory sell-through)
The share of the ad inventory you had available that you actually sold.
The fork, why two teams get different numbers
Sell-through and fill rate are cousins and get swapped. Fill rate asks "of what
we tried to fill, what filled?"; sell-through asks "of what we could have sold,
what did we sell?" The fork is the denominator of "available." DIRECT sell-
through = directly-sold impressions / forecast available impressions for guaranteed
inventory, the number a direct-sales team is measured on. TOTAL sell-through
folds programmatic/open-market impressions into both the sold count and the base,
which is nearly always high because programmatic clears almost everything at some
price. There is also a FORECAST fork: available impressions is a projection, and
whether you divide by forecast or by realized impressions changes the rate.
Sales quotes direct sell-through (their quota); the CRO may quote total to claim
the site is monetized.
The trap
Blending programmatic into sell-through makes a poorly-sold site look sold-out: the open market clears remnant at pennies, so total sell-through can read 95% while direct (premium, high-CPM) sell-through is 45% and the revenue mix is mostly cheap programmatic.
- The full trap, worked on a real export
- Every formula variant, spelled out
- The reconciliation anchor, what to tie it to and when to refuse
Reference: IAB inventory/yield convention (reference); ad-operations practice (no single standards body)