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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