<b>First-price auctions removed the anchor — and buyers never replaced it</b>

<b>First-price auctions removed the anchor — and buyers never replaced it</b>

When the open exchange moved to first-price (you pay exactly what you bid, versus second-price where you paid one cent above the runner-up), the industry framed it as a transparency win. The deeper change was the loss of a free reference price.

The mechanism:
— Under second-price, the auction itself told you the market's valuation: the price you paid was the next-highest bid. That was a continuous, free signal of competitive demand.
— Under first-price, the clearing price equals your own bid. The auction reveals nothing about what others would have paid.
— So every buyer must now estimate the clearing distribution privately, from their own win/loss history — data that is censored, because you never see the prices of auctions you lost.

This is why two DSPs can pay wildly different CPMs for identical inventory: each is reconstructing a hidden price surface from a different, biased sample of its own outcomes.

Implication: bid shading exists precisely to rebuild the anchor that second-price gave away for free. The quality of your shading is the quality of your private price model — and a thin spender on a segment has a worse model than a whale, structurally.

Why it matters: in first-price, information asymmetry is the durable edge. Buyers with more volume on a path estimate its clearing price better and overpay less — a compounding advantage that has nothing to do with creative or targeting.