When to include them, when not to, and how to interpret them if you do

When teams begin working with Marketing Mix Modeling (MMM), one of the first questions that comes up is:

“What should we do with channels that don’t have media spend?”
Think: SEO, Organic Social, or Email (when not tied to paid sends).

These channels matter for your go-to-market motion, but because MMM is fundamentally built on understanding the relationship between spend, impressions, and conversions, organic or zero-spend channels behave differently in the model. Understanding how and when to include them helps you get a cleaner, more actionable read from your MMM.

This article walks you through:

1. Should you include zero-spend channels in an MMM?

2. What are the tradeoffs when you do?

3. If included, how should you interpret them?

1. What do we mean by “zero-spend channels”?

Zero-spend channels are marketing activities where you’re not buying impressions or clicks but generating them organically. Examples include:

• SEO / Organic Search

• Organic Social

• Email, when there is no paid element

• Community / Brand-owned channels

These channels create real value — often substantial value — but their motion is not spend-driven.

📌 Why this matters for MMM:
Paramark MMMs are designed to understand the relationship between spend → impressions → conversions. When spend is missing, the model must interpret the activity differently, which introduces unique considerations.

2. Should you include zero-spend channels in your MMM?

There is no universal yes/no — it depends on why you want them in the model and how they function in the funnel.

Below are the most common motivations and how we think about them.

Reason 1 — You want a more accurate baseline (good reason)

Some customers include organic channels because they don’t want that activity “hidden” inside baseline, which represents volume the business would have received with no paid marketing (or channels not accounted for in the MMM) .

If Organic Search or Email is a major part of your acquisition, leaving it out can inflate baseline and make the model feel incomplete.

When to include:
✔ If the channel meaningfully drives conversions
✔ If you want a more “true” baseline
✔ If the metrics are stable, well-defined, and consistently available

When not to:
✘ If the data is noisy, inconsistent, or poorly defined
✘ If including it creates more confusion than clarity

Reason 2 — You want to see organic contributions for reporting or completeness (situational)

Some customers simply want all channels represented so everything appears in one place.

Worth including only if:

• The channel is strategically important

• The metric you provide is consistent and interpretable

• You understand the model won't quantify “incrementality” in the same way it does for paid channels

If those conditions aren’t met, including it may clutter the model without adding insight.

Reason 3 — You intend to take action on the channel (often not ideal)

Customers sometimes want to “optimize SEO” or “increase email sends” based on MMM outputs.

This is usually not how MMM should be used for zero-spend channels.

Why?

• There is no spend variable to optimize.

• The model is observing correlation, not causal lift from investment.

• Changes in organic channels are driven by content quality, frequency, ranking, or CRM strategy — not a spend dial.

If you want to optimize these, experimentation or channel-specific analytics are far better tools.

3. The key considerations before adding zero-spend channels

A. What is the channel’s role in your GTM funnel?

Email could mean prospecting, conversion, or retention — each behaves very differently.
Organic social could be awareness-driving or community-driven.

The MMM needs a single, clean, stable metric for each.

B. Will including it help or hurt actionability?

If a channel can't be “dialed up” through spend, the MMM should not be used to guide scale decisions for it.

C. Is the data high-quality and consistent?

MMM is particularly sensitive to:

• Sharp discontinuities

• Definitions that change over time

• Channels that don't vary much week to week

D. Is the goal avoiding misplaced credit?

Some customers include organic so paid channels don’t “steal credit” for conversions truly driven by SEO or Email.
This is a valid reason — but only if the organic metric accurately captures the underlying activity.

4. If you do include zero-spend channels — how should you interpret the results?

When included, organic or zero-spend channels behave differently in the model:

1. They will not have a spend-driven response curve

The model is reading correlations between organic activity (e.g., pageviews, opens) and conversions — not measuring marginal returns to spend.

So instead of:

“For $10K more, you get X more conversions,”

you’ll get:

“When organic traffic is higher, conversions tend to rise.”

It’s a relationship, not a lever.

2. They help prevent false attribution to paid channels

Including meaningful organic metrics prevents performance channels from absorbing credit that belongs to organic efforts. This stabilizes the model and gives a more realistic view of paid channel incrementality.

3. Their contribution should be interpreted qualitatively, not as an investment lever

An organic channel’s “incrementality” in the MMM is showing:

• The share of conversions correlated to that metric

• The portion of volume not driven by paid media

It’s not telling you:

• How much to “spend”

• How to allocate budget

• Whether to “increase investment”

4. They often absorb long-term brand effects

Organic Search volume or Email engagement frequently captures:

• Brand strength

• Customer familiarity

• Word of mouth

• Category demand

In that sense, they become helpful proxies for long-term brand impact — especially in models where brand input is otherwise hard to quantify.

5. Our recommended decision framework

Use this simple rubric to decide:

✅ Include the channel if:

• It has a meaningful, consistent influence on conversions

• The metric is stable and well-defined

• You want a cleaner baseline

• You are not planning to “optimize” the channel using the MMM

• It’s strategically valuable to see the channel represented holistically

❌ Do not include the channel if:

• The metric is noisy or inconsistently defined

• The activity is weakly tied to acquisition

• The channel’s inclusion causes confusion about actionability

• You want the MMM to guide tactical changes for this channel

6. Summary — Paramark's perspective

Here’s the simplest way to think about it:

Zero-spend channels absolutely matter — but they don’t behave like paid channels in an MMM.
Use them to make your baseline more correct, your funnel more complete, and your model more representative of how your business works.

Just don’t expect the MMM to tell you how to scale them — that’s the wrong tool for the job.

A great MMM:

• Helps you understand how paid media drives incremental conversions

• Separates paid from organic influence

• Gives a true read on your marketing efficiency

And thoughtful inclusion of organic channels can make the model more correct, as long as the expectations are set appropriately.

Want to learn more about marketing mix modeling? Check out other Paramark marketing mix modeling articles here