The question every creative review should answer: when an ad scores well on a cheap upper-funnel signal — thumbstop, hold rate, CTR, cost-per-engagement — does that same ad go on to acquire customers cheaply, earn more cash, and get scaled? We grouped every ad with $1k+ spend over 14 days and measured the answer per metric.
Grouping ads into best / middle / worst thirds by each metric (spend-weighted), the best-engagement third consistently posts a 24–43% lower CAC than the worst third — and earns far more cash. CTR is the cleanest predictor (best third $195 CAC vs worst $341, a statistically significant relationship). Thumbstop and hold rate point the right way but are noisier per-ad. Cost-per-engagement is the least reliable — use it last.
Why grouping, not dots: a single ad's 14-day CAC is noisy (few conversions, outliers), so an ad-by-ad scatter shows almost nothing. Bucketing into thirds and weighting by spend cancels that noise and reveals the real signal — which is why the headline lives in the bars, not the dots.
Ranked by how reliably the metric separates a good CAC from a bad one. "CAC gap" = best-third CAC vs worst-third CAC (more negative = stronger predictor).
| Engagement metric | Better when | Best⅓ CAC | Worst⅓ CAC | CAC gap | Rank corr (ρ) | p-value | Verdict |
|---|
For each metric: ads split into best / middle / worst thirds, then the spend-weighted CAC, cash, and ROAS of each group. If the metric predicts performance, the green (best) bar should sit well below the red (worst) bar.
Every engagement metric and outcome for the 20 highest-spend ads. Note how the high-CTR, high-thumbstop video ads cluster at the lower CACs — and how Google Search ads (no video metrics) are a separate species entirely.
| Ad | Type | Spend | Thumb | Hold | CTR | Cost/Eng | NC | Cash | CAC |
|---|
It separates good CAC from bad CAC more cleanly than any other engagement metric here — and you can read it days before CAC stabilizes. A high-CTR new ad is your best early bet to scale.
They point the right way (better hook/hold → lower CAC) but are noisy on any single ad. Good for diagnosing why a creative underperforms, not as a solo scale/kill trigger.
It showed the weakest and least consistent link to CAC. Cheap likes ≠ cheap customers. Deprioritize it in scorecards.
The best-engagement third also absorbed the most budget — Meta is voting the same way. That's confirmation, but also a reason to read these as associations, not proof of pure cause.