Detecting repeated exposure across line items

Two line items can each report unique reach while including some of the same people. To detect repeated exposure, compare deduplicated campaign-level unique reach with each line item’s unique reach over the same dates and within the same campaign boundary.

First identify the line items to compare, noting any shared audience, creative or objective. Record each item’s unique reach, then add those figures and compare the total with deduplicated campaign-level unique reach.

In Display & Video 360, build the check in Report Builder with the metric “Unique Reach: Impression Reach”. Run it once with the Line Item dimension and once with only the Campaign dimension, using the same advertiser, date range and campaign filter. Adding “Unique Reach: Average Impression Frequency” shows how often each group was reached.

Report Builder also lists “Unique Reach: Duplicate Impression Reach” and “Unique Reach: Exclusive Impression Reach”, each with a per cent version. Where the report accepts them, add them to the line-item rows so duplicated and exclusive reach are reported alongside each item rather than inferred.

With consistent dates and boundaries, campaign-level reach should be at least as large as any one line item’s reach and no greater than the sum of the item reaches. If it is lower than that sum, some people were counted in more than one line item.

A worked example in thousands: line item A reaches 7 thousand and line item B reaches 5 thousand, so the items sum to 12 thousand. If the campaign row shows 9 thousand, then 3 thousand reach counts were duplicated across the two items. The campaign figure sits between the larger item and the sum, as expected.

The difference between the sum of item reaches and campaign-level reach represents duplicated reach counts; it is not necessarily the number of distinct people who saw multiple items. Aggregate reach figures also do not identify which line items shared those people.

Keep the two reports comparable. Use the same date range and the advertiser’s reporting time zone for both runs, and include only impressions inside the campaign boundary. Export both runs as CSV and keep them with the date range and filters used, so the subtraction can be repeated outside the platform.

DV360 offers frequency controls and measurement options, but a frequency cap or generic measurement view does not prove cross-line-item duplication. Use a combined campaign view only if it explicitly deduplicates reach across the selected line items, then compare it with each item’s view for the same dates.

A higher-level cap may cover several line items, but meeting a cap does not confirm that reach has been deduplicated. Check that the items being compared sit under the same campaign control; separate advertisers, platforms or identifiers may leave repeated exposure outside that boundary.

If no deduplicated combined figure is available, line-item totals cannot confirm person-level overlap. Mark overlap as unconfirmed rather than treating the sum of item reaches as campaign reach; if overlap is confirmed, review the shared campaign control or audience exclusions and repeat the comparison.

Key Facts on Repeated Exposure Detection