Discrepancy

How it works

Two systems rarely count the same thing in the same way. The common sources of a gap are:

• Different definitions. A store download and a first open are both called an install. An MMP counts the first open.
• Different dates. One system may file a conversion under the day of the ad click, the other under the day of the install.
• Different windows. A longer attribution window credits more conversions to ads.
• Different credit rules. An ad platform sees only its own ads and may claim a conversion that the MMP credited to another channel under last-touch attribution.
• Time zone and currency settings. Days are cut at different hours and revenue is converted at different rates.

When it matters

A steady gap that you can explain is something to note and move on from. Investigate when the gap changes abruptly, when one event is missing on one side, or when the two systems disagree on direction, with one showing growth and the other a decline. During a migration, a discrepancy between the old and the new MMP is the main thing a parallel run exists to find.

How it relates to attribution

Attribution is a set of rules for assigning credit, so two sets of rules produce two answers. Pick one system as the reference for budget decisions and use the other as a check. After you change MMPs, expect the gap to each ad platform to shift, and record the new baseline in the first week described in reconnecting ad channels.