There are at least 28% more conversions in this budget. And they’re yours.
A full quarter of campaign data, analyzed by day of week under multi-touch attribution, shows a 140% gap in cost per conversion between the best-performing day and the worst. The budget allocation does not reflect this gap. Shifting a modest portion of spend from the worst day to the best produces hundreds of additional conversions without any change in total spend, creative, or strategy.
This is what multi-touch attribution is designed to surface. Last-touch models do not show it.
The Data
The analysis covers one quarter of a national advertiser’s campaign data, segmented by day of week. All figures reflect MTA cost per conversion — the full spend allocated to a day divided by the MTA-attributed conversions originating from that day’s media activity.
| Day | MTA CPC | Last-Touch CPC | Spend | MTA Conversions | Conv Rate |
|---|---|---|---|---|---|
| Monday | $33.00 | $67.25 | $95,730 | 2,901 | 50.9% |
| Tuesday | $29.78 | $80.56 | $93,504 | 3,140 | 63.0% |
| Wednesday | $37.16 | $89.80 | $91,183 | 2,454 | 58.6% |
| Thursday | $18.85 | $63.83 | $90,527 | 4,803 | 70.5% |
| Friday | $45.37 | $92.89 | $135,793 | 2,993 | 51.2% |
| Saturday | $25.43 | $51.84 | $87,934 | 3,457 | 50.9% |
| Sunday | $19.39 | $46.43 | $85,756 | 4,422 | 58.2% |
| Total / Avg | $28.15 | $67.89 | $680,429 | 24,169 | 58.5% |
Thursday converts at $18.85. Friday converts at $45.37. Friday received 20% of the total weekly budget — more than any other day — and produced the worst cost per conversion of any day in the week. Sunday, the second-best performer at $19.39, is underallocated relative to its efficiency.
The Gap That Last-Touch Can’t See
Last-touch attribution assigns conversion credit to the final touchpoint before purchase. Under a last-touch model, the Thursday/Friday gap looks different: Thursday is $63.83, Friday is $92.89. The directional signal is the same, but the magnitude is compressed. More importantly, last-touch provides no mechanism for tracing the full cost of producing that conversion — only the cost of the last click. Budget decisions made on last-touch data will miss the full efficiency story.
Multi-touch attribution distributes credit across the complete consumer path, weighting each touchpoint by its actual contribution to the conversion. The result is a cost-per-conversion figure that reflects the full media investment required to produce the result — not just the investment in the final step. The Thursday MTA CPC of $18.85 incorporates the full upstream path; the last-touch number does not.
This distinction is not theoretical. The 140% efficiency gap between Thursday and Friday — $18.85 vs. $45.37 — is only visible at its full magnitude under MTA. A budget allocation decision made using last-touch data would still identify Friday as relatively inefficient, but would understate the opportunity by roughly half.
The Reallocation Opportunity
Given the efficiency gap, a natural question is how much value a reallocation could recover. Two scenarios illustrate the range:
Floor scenario: Shift 20% of Friday’s budget ($27,159) to Thursday. At Thursday’s observed MTA CPC of $18.85, that spend produces approximately 1,440 additional conversions on the reallocated budget — compared to the 598 conversions the same dollars would have produced at Friday’s rate. Net gain: approximately 842 conversions. Total spend: unchanged.
Ceiling scenario: Shift 50% of Friday’s budget across Thursday and Sunday (the two highest-efficiency days). At blended Thursday/Sunday efficiency, the reallocated $67,897 produces approximately 3,500 conversions — compared to the 1,496 those dollars produced on Friday. Net gain: approximately 2,055 conversions. Total spend: unchanged.
28% more conversions. Same budget. One reallocation.
Why 28%, Not 140%
An unconstrained optimization — moving Friday’s entire budget to Thursday at current efficiency rates, with no diminishing returns and no audience saturation — would project a 141% conversion lift. That number is mathematically correct and strategically wrong.
Thursday’s efficiency exists partly because it is not over-allocated. Push significantly more spend into any single day and efficiency will decay: audience pools thin, frequency caps are reached sooner, and the incremental consumer reached at high spend levels is less likely to convert than the consumer reached at moderate spend levels. The $18.85 CPC reflects Thursday at its current allocation, not Thursday at five times its current allocation.
The 28% floor estimate accounts for this. It assumes a modest reallocation — 20% of one day’s budget — that is unlikely to materially alter Thursday’s efficiency profile. It also produces a number that is defensible in a budget review: the assumptions are explicit, the math is transparent, and the estimate would need to be wrong by a factor of two to produce no improvement at all.
A number you can defend and will move on is worth a lot more than a bigger number that stays in a deck.
What This Requires
Day-of-week efficiency analysis of this kind requires multi-touch attribution data at the path level — not platform-reported conversions, and not last-touch credit. The analysis above uses C3 Metrics’ MTA output, which attributes each conversion across the full upstream path using actual media spend and observed consumer behavior.
Platform-side reporting does not produce this analysis. Each platform reports its own conversions, using its own attribution window, with no visibility into what other channels contributed to the same conversion. Aggregating platform-reported day-of-week data does not produce a cost-per-conversion figure that reflects the full spend required to generate the result — it produces a collection of overlapping, self-reported claims.
Independent MTA programs produce a single, consistent attribution across all channels and all days, making cross-day efficiency comparisons meaningful. This is one of the structural advantages of path-level measurement: it makes allocation questions answerable in a way that platform-reported data cannot.
Day-of-week efficiency analysis is a standard output of C3 Metrics’ attribution programs. The same methodology that surfaces the Thursday/Friday gap is available across channels, dayparts, creative units, audience segments, and geographic markets — producing a full picture of where the budget is working and where it is not. Most programs surface multiple reallocation opportunities of similar magnitude within the first quarter of data.