Glossary · Marketing Engineering
Geo-Lift Testing
also: geographic split test · geo experiment · market holdout
Definition
Geo-lift testing is an experimental design that randomizes marketing treatment across geographic markets (DMAs, metros, countries) to measure incremental impact when user-level randomization is infeasible. Synthetic control and open-source libraries like GeoLift construct matched control markets from pre-period covariates.
User-level A/B tests fail for TV, radio, OOH, and brand campaigns because exposure is unobservable per user. Geo-lift solves this by treating markets as units: run the campaign in treatment markets, withhold in synthetic or matched controls. Meta's open-source GeoLift library automates market matching via time-series regression; Google's CausalImpact adds Bayesian uncertainty. Minimum detectable effect depends on market variance and campaign size — typically 8–15% lift is detectable at large weekly spend with 4 treatment and 20 control markets.
Essays on this concept
- Marketing Strategy
Brand vs. Performance: A Portfolio Optimization Framework Using Markowitz Theory for Marketing Budget Allocation
Finance solved the allocation problem in 1952. Marketing still argues about it in 2026. Markowitz's portfolio theory — applied to marketing channels instead of stocks — reveals an efficient frontier that makes the brand-versus-performance debate quantitatively resolvable.
- Marketing Engineering
Incrementality Testing at Scale: A Geo-Lift Framework for Measuring True Campaign Impact
Half your marketing budget is wasted. The classic joke, except now we can identify which half — geo-lift experiments measure what would have happened without the campaign, not just what happened with it.
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