Short-term vs. long-term effects of in-store advertising

What happens after the flight ends? Most campaign reports stop there, measuring sales during the campaign and perhaps a week or two after. That captures short-term effects. Long-term advertising effects, such as lasting changes in how often a brand is chosen or how well it's recognized, play out over months and are much harder to measure. Both matter, and they call for different methods and different levels of confidence.

The honest position is that short-term effects can often be measured reasonably well, and long-term effects usually can't be measured precisely from a single campaign.

What are short-term effects?

Changes in sales during and shortly after a campaign. For in-store media, that usually means comparing sales of the advertised products in advertised stores with similar stores over the flight and a few weeks after.

These are the effects most campaign reports describe. They're easier to measure because they're close in time to the advertising, and fewer other things change in the meantime.

Short-term effects include any post-campaign dip, where sales fall below normal after being pulled forward. Measuring a few weeks after the flight catches that.

Short-term measurement also has a practical advantage: it fits the planning cycle. Brand teams usually decide on the next campaign within weeks, and short-term results arrive in time to inform that decision.

What are long-term effects?

Changes that persist or build after the campaign ends. A shopper who tried a product because of an ad and kept buying it. A brand that became more familiar in a neighborhood and is chosen more often months later. Increased brand awareness that supports future campaigns.

These effects are plausible and widely discussed in the industry. They're also hard to isolate. Over months, many other things change: prices, distribution, competitor activity, seasons. Separating a single campaign's lasting contribution from all of that is difficult.

What can in-store data show about the long term?

Some things, with care. Comparing advertised and comparison stores for several months after a campaign can show whether a gap persisted. If advertised stores continued to sell more of the product long after the flight, that's suggestive of a lasting effect.

But the longer the window, the more likely the store groups diverge for other reasons. A distribution change in one group, or a local event, can create or erase a gap. The evidence weakens as time passes.

A practical middle ground is to track the same store groups for a few months after each campaign and note anything that changed in either group along the way. That won't settle the long-term question on its own, but it builds evidence campaign by campaign.

Repeated campaigns help. If a brand runs in-store media over a year or more, comparing stores with consistent exposure against stores without it gives a broader view. Methods like marketing mix modeling, which estimate the contribution of many factors over long periods, are designed for these questions.

How should both be reported?

Separately and with different confidence. Report short-term effects with their comparison and range. Report any long-term observations as suggestive, with the caveats that apply.

Don't extrapolate. A short-term effect doesn't imply a long-term one of any particular size. Claiming that a campaign's effect will continue or grow, without evidence, overstates what's known.

Say what would change your view. If advertised stores still lead comparison stores three months on, note it. If the gap closes within weeks, note that too. Both are useful findings.

Build a record. Over many campaigns, patterns emerge that no single report can show. Keeping consistent measurement across campaigns is the most practical way to learn about long-term effects. To discuss measurement for an ongoing program, contact the NRS Digital Media team, or visit the NRS Digital Media site.