Spektre, the media quality platform, today announced the results of a display campaign conducted in partnership with Kees Smit. The study shows that quality signals reliably predict which inventory actually converts and which inventory simply absorbs budget.
For the campaign, Spektre’s Advertiser Suitability & Performance Index (ASPI) was compared with actual campaign results across 2,092 display domains. ASPI scores media quality on a scale from 0 to 100: the higher the score, the higher the quality.
The outcome was clear: the campaign achieved an ASPI score of 77 out of 100. In total, 95% of all conversions came from high-quality inventory (ASPI 60+), while 43% of total budget went to domains that produced no conversions and did not meet the quality standard.
Thijs Visser, Co-founder at Spektre
The data shows a strong concentration of sales across a limited number of high-quality domains, including ad.nl, marktplaats.nl, and funda.nl. On average, these domains converted 258× more efficiently than the rest of the inventory combined.
7× more efficient above ASPI 60
High-quality inventory needed 7x fewer impressions per sale
40× difference at the extremes
The top segment (ASPI 90–100) needed 40x fewer impressions per sale, compared with the lowest segment (ASPI 0–20).
773 domains formed the trusted core
Domains combining multiple quality characteristics delivered 87% of all sales, 18× better than the rest of the inventory.
Alongside the quality segmentation, a specific fraud pattern also came to light. Five domains in the campaign turned out to be part of the same MFA network: 52 nearly identical sites, built from one template and one hidden owner, each with its own name and topic to avoid detection.
Impressions were absorbed by five look-alike domains without offering visitors relevant content.
Because Kees Smit optimizes for quality, exposing these clusters creates immediate value: budget that would otherwise disappear into a network of look-alike sites can now be prevented.
Melvin Harms, at Kees Smit
The advantage of high-quality inventory does not sit in one isolated step; it compounds across the full marketing funnel. Inventory with an ASPI score of 60 or higher performs 4.5 times better at generating clicks than low-quality inventory, and then converts those clicks 1.5 times more effectively into sales.
4.5×
better at generating clicks
1.5×
more effective at driving sales
7×
advantage from impression to sale
From impression to sale, that adds up to a sevenfold advantage. Low-quality inventory may still produce clicks, but those clicks are simply less purchase-oriented. That has direct consequences for how performance is evaluated: optimizing on a single metric is unreliable. In this campaign, some of the worst-converting inventory showed above-average CTR despite clear risk signals such as missing consent frameworks and a high ad ratio. Only by analyzing quality signals together does true performance become visible.