Most Ad Spend Concentrates In A Fraction Of Traffic Sources, Bitmedia.io Analysis Finds

A small share of traffic sources is responsible for the vast majority of ad impressions and spend, but those same sources do not generate clicks at the same rate, according to an analysis of more than 900 advertising campaigns by digital advertising platform, Bitmedia.io.

The analysis found that just 10 per cent of traffic sources generated 77 per cent of ad impressions and absorbed 71 per cent of spend – yet produced only 57 per cent of clicks.

The research covered 425 traffic sources, 85,458 campaign-source combinations, more than 3.12 billion impressions and 10.5 million clicks.

Concentration increases at the top

The concentration becomes more pronounced when the top 20 per cent of traffic sources are examined. That group accounted for 87 per cent of impressions and 83 per cent of spend, leaving the remaining 80 per cent of sources competing for less than 17 per cent of the total budget.

Bitmedia.io notes that concentration itself is not inherently problematic. Large traffic sources often play an important role because they provide the scale advertisers need.

The issue, according to the analysis, is that the number of sources included in a campaign can create a misleading impression of how diversified the actual media buying is. A campaign can technically use a broad mix of publishers and placements while most of the spend still flows through a small number of them.

Clicks distributed more broadly than impressions

The gap between delivery and response is where the data becomes more revealing.

The remaining 90 per cent of sources received only 23 per cent of impressions but collectively generated 43 per cent of clicks. While the top 10 per cent of sources dominated delivery, clicks were distributed more broadly across the traffic mix.

The pattern held when the top 20 per cent were examined. That group controlled 87 per cent of impressions and 83 per cent of spend but generated 74 per cent of clicks.

Bitmedia.io cautions that the dataset does not include conversions, revenue or customer value, so click contribution should not be treated as a direct measure of traffic quality. What the numbers do show is that scale and audience response are distributed differently.

Hidden allocation risk

For advertisers, the analysis points to what Bitmedia.io describes as a hidden concentration problem. An overall click-through rate, cost-per-click or cost-per-thousand-impressions figure can appear stable while masking a campaign in which a few sources determine most of the spend and impressions.

That becomes particularly relevant when budgets are scaled, reduced or reallocated. If more than 70 per cent of spend sits inside just 10 per cent of traffic sources, a campaign-level decision can effectively move the majority of the budget without revealing how differently those sources contribute to delivery and response.

Source-level visibility matters

The analysis suggests that for marketers trying to understand where advertising budgets are actually going, source-level contribution data can be just as important as campaign averages.

A broad source mix does not automatically mean a diversified budget. Bitmedia.io argues that marketers need to examine how spend, delivery and response are distributed across individual sources before making allocation decisions.

The key question, according to the research, is not simply how many traffic sources a campaign uses but how much of the budget, delivery and response each source actually contributes.

Last Updated on September 17, 2026 by Nick Ross