Engagement Spend & CAC — Hypothesis Test

The chart you asked for

Engagement spend vs CAC vs CPM — week by week

Bars = share of Meta spend going to genuinely non-conversion campaigns (awareness / engagement / reach / traffic / video-views, per Meta's objective field). Lines = blended D2C CAC (Daily Spend Tracker: spend ÷ Shopify new customers) and Meta CPM. If the hypothesis were right, the bars and the CAC/CPM lines should move together. They don't — the bars vanish while the problems continue.

CAC here is the Daily Stand blended D2C number (all channels — Meta, Google, YouTube, podcast, affiliate, agency est. — ÷ Shopify new customers), the figure the exec team watches. It has been above the $90 target the entire window and is now accelerating: $115 (May 25) → $127 (Jun 1) → $131 (Jun 8), on new customers down to ~350/day. Genuine engagement spend ran only in the second half of March and was switched off entirely from early April — so the June CAC spike happened with zero engagement spend running.

A correction worth flagging

What "engagement spend" actually is

First pass, I classified campaigns by name and the number looked like 2.7% of spend. That was wrong — it swept in MUD_CPP_D0_TopAds ($119k), which Meta's objective field shows is a conversion (sales) campaign, not a brand boost. Cross-checking every campaign against Meta's real objective field, the truth is smaller and clearer:

The math

Correlation: none — or backwards

Across the 12 weeks, here's how engagement's share of spend correlates with the metrics it was supposed to be hurting. (+1 = move together, 0 = unrelated, −1 = move opposite.)

Engagement % vs CAC

−0.22

If anything, slightly inverse — engagement ran when CAC was lower, not higher.

Engagement % vs CPM

−0.70

Strongly negative — the opposite of the fear. CPM was lowest when engagement was highest.

Engagement % vs Volume

+0.18

No meaningful relationship. Engagement spend didn't lift or suppress new-customer volume.

The timing settles it. Engagement spend was switched off entirely after early April. The worst CAC weeks — May 18 ($108), May 25 ($115), Jun 1 ($127), Jun 8 ($131) — all ran with zero engagement spend. There is nothing to lag, and nothing running, during the period CAC actually broke.

Reading it honestly

What fits the theory, and what kills it

The March ramp FITS

Engagement spend did ramp Jan → Feb → March (peaking ~$46k for the month, 4.8% of Meta spend in its top week), and March was a worrying month. This is the one genuine piece of support for the hunch — and why it was worth checking.

CPM moved the wrong way AGAINST

The core fear is engagement → higher CPMs. But CPM was at its lowest ($24) during the March engagement peak, and only spiked ($44–48) after engagement was switched off. That's the seasonal summer ramp, not pollution. Correlation −0.74.

Early May had zero engagement AGAINST

The "we scaled engagement in early May" memory doesn't survive the objective field — that spend was MUD_CPP_D0_TopAds, a conversion campaign. Real engagement spend in May was $0. The early-May CAC slide had nothing to do with brand boosting.

Too small to move CAC SCALE

At its peak, real engagement was ~1% of total paid spend, and zero for half the window. Even if every engagement dollar were pure waste, it mathematically cannot move blended CAC the way the lines moved.

Volume

New customers vs engagement spend

Same story on volume. Weekly new customers (Shopify) don't rise with engagement spend or fall when it's cut — the relationship is flat (+0.05). Volume softened into June while engagement had been off for two months.

If not engagement, then what

What actually drove the bad weeks

The CAC pressure lines up with things we've already documented — none of which is engagement spend, which was off entirely during the worst stretch:

Seasonal CPM ramp. Meta CPM climbed from ~$24 (March) to ~$48 (early May) — the predictable summer auction pressure, and the single biggest mechanical driver of higher CAC.
The conversion-rate gap. Site CVR ran ~15–20% below last year through this window — the structural driver from the "Why is CAC at $120" teardown. Cheaper traffic wouldn't have fixed a collision problem.
Volume collapse, not cost. New customers fell to ~350/day in June (2,481 the week of Jun 8, lowest in the window) even as CPM eased to ~$32 — so June's $131 CAC is a denominator problem (too few customers), not expensive media. That's a demand/CVR story, not a pollution one.
Engagement was switched off. From mid-April through June, non-conversion spend was $0. The bad weeks can't be caused by spend that wasn't running.

Honest limits

What this can — and can't — prove

Using Meta's objective field removes the classification guesswork, but a couple of limits remain:

Small sample. 12 weekly points, with engagement non-zero in only four of them. Strong enough to rule out a meaningful effect; not fine enough to detect a tiny one.
Campaign-level, not adset-level. A conversion campaign could in theory contain an engagement-optimized adset. This view is campaign-objective; it wouldn't catch engagement hiding inside a sales campaign.
The mechanism isn't directly observed. Pixel/audience pollution would only operate if engagement campaigns share the pixel and custom/lookalike audiences with conversion campaigns. We tested the outcome (CAC/CPM), not the plumbing.

If you want total certainty

The one clean test

Given engagement is ~1% of spend and already off, the practical answer is "this isn't your CAC problem." If you still want to close it out:

Check the plumbing (free, 30 min). Confirm whether engagement/awareness campaigns share the same pixel + custom/lookalike audiences as conversion campaigns. If siloed, pollution is mechanically impossible.
Reframe the real question. The sharper question isn't "does engagement hurt CAC" (it doesn't, measurably) — it's whether ~$78k / 6 months on brand boosting earns its keep in retail lift + brand, or should move to conversion. That's a value decision, not a pollution one.

The underlying numbers

Weekly detail

Week of	Engagement $	Eng % of Meta	Blended CAC	Meta CPM	New customers

CAC & new customers: Mud Daily Stand — blended D2C, all channels (Meta, Google, YouTube, podcast, affiliate, agency est.) ÷ Shopify new customers, Pacific dates. Monthly blended CAC: Mar $98 → Apr $94 → May $101 → Jun (MTD) $129. Engagement spend: Northbeam campaign spend, filtered to campaigns whose Meta objective is non-conversion (awareness / engagement / reach / traffic / video-views). CPM: Meta Ads, weekly. Monthly verified engagement: $7k (Jan) → $23k (Feb) → $46k (Mar) → $1.6k (Apr) → $0 (May) → $0 (Jun). Six-month total $77,790 ≈ 1% of paid spend.