Detection: Reported conversions dominated by 1-day-view attribution

Key: attribution_one_day_view_overdependent Severity: Medium Confidence: 75% Shipped: v1.2, May 2026 Runtime: Requires Meta OAuth (attribution-window breakdown fields are Meta-API-only).

What this detection looks for

We fire one account-level finding when all of these are true:

Both account_purchases_1d_view and account_purchases_total are populated on the snapshot
account_purchases_total is positive
Account monthly spend projects to ≥ $5,000
1-day-view share > 40% of total attributed purchases

Why this matters

Sam Tomlinson's 2026 audit and Cody Plofker (October 2025) both surface 1DV-dominance as one of the strongest signs that paid Meta is cannibalizing rather than incrementing. The default Meta attribution setting includes 1-day-view, but accounts at scale should treat 1DV purchase share above 40% as a flag — a real geo holdout would usually show those conversions happen with or without the ad.

This is the inverse of attribution_window_mismatch:

attribution_window_mismatch fires when an account is configured for 1-day-click on a high-spend account that should be using 7-day click.
attribution_one_day_view_overdependent fires when actual reported purchases are dominated by 1-day-view — a different attribution-misalignment story.

Both rules surface attribution mis-calibration; they're complementary.

How we estimate the recoverable dollars

overrun = (1dv_share − 0.40) / 0.40
wasted = account_spend × 0.25 × overrun
monthly_recoverable = wasted × 30 / audit_days

The 0.25 waste factor and the proportional overrun formula reflect Tomlinson's framework: every 10 points above the 40% threshold corresponds to roughly 6% of spend on non-incremental conversions.

What would change our mind

A real holdout test ruled differently. If you've run a geo holdout that proved your 1DV-attributed conversions are incremental, trust the test over the heuristic. The rule is a structural pattern; an incrementality test is direct measurement.
Brand awareness campaign with measurable lift. If a significant share of your spend is a deliberate brand-awareness push, 1-day-view share will be naturally higher and partly reflects real upper-funnel lift. Treat the dollar estimate as a ceiling.
High-AOV considered-purchase products. Products with long consideration windows (mattresses, appliances) genuinely see 1-day-view conversions that complete via a click days later. Cross-reference with click-attributed conversion timing.

What to do about it

Run a geo holdout test. Pause Meta in 1–2 markets for 4 weeks; compare revenue to comparable markets where Meta keeps running. The difference is your true incremental ROAS.
If the holdout confirms 1DV is cannibalization, narrow your attribution setting to 7-day-click-only and watch the reported ROAS drop — that's the truth that was hidden in the 1DV column.
Rebalance budget toward upper funnel. If 1DV-attributed purchases are mostly non-incremental, the spend that produced them is reaching customers who'd have bought anyway. Shift that budget toward true prospecting.

References

Sam Tomlinson: "The Ultimate Meta Ads Account Audit, Part II"
Cody Plofker (X, October 2025): on 1DV cannibalization
Haus.io: "Understanding Meta Incrementality Testing"