<b>How much does your attribution depend on a number nobody debates — the lookback window?</b>

<b>How much does your attribution depend on a number nobody debates — the lookback window?</b>

More than almost any model choice, and it's usually set once and forgotten.

<b>The mechanic</b>

The lookback (or conversion) window defines how far back from a conversion you'll look for qualifying touchpoints — 1 day, 7 days, 28 days, 90 days. Every touch outside it is invisible to your model.

<b>Why it quietly dominates results</b>

Window length acts as a hidden weighting on channel mix. A short window structurally favors lower-funnel, click-heavy channels (search, retargeting) and erases upper-funnel touches that happened earlier. A long window inflates the credit of any always-on channel that's simply present in most journeys. You can change which channel "wins" by editing one dropdown, with no change to actual behavior.

<b>The nuance</b>

There is no universally correct window — it should match your real purchase-consideration cycle. An impulse e-commerce buy and a six-month B2B deal cannot share a 7-day window honestly. Mismatched windows are a major reason cross-channel reports contradict each other.

<b>What to actually do</b>

— Derive the window empirically: look at the distribution of time-to-conversion across your actual paths, and set it near the 80th-90th percentile of genuine consideration time.
— Run sensitivity analysis: rerun your model at 7, 14, 30, 90 days and see which conclusions survive. Conclusions that flip with the window aren't robust.

Bottom line for practitioners: the lookback window is a modeling assumption disguised as a setting. Test its sensitivity before you trust any channel ranking built on top of it.