Category dilution? Is it a thing in 2025/2026?

[WilliamGMBE]

Wanted to share a study we did about category dilution. A common question we had from our customers is whether adding categories hurt my current ranking, or will adding new categories bring more traffic?

We did a study, you can find it here: Category Dilution Study

We have included the raw data and interactive graphs in the link above so you can check it out for yourself. In short, we found:

• Adding relevant categories did not hurt existing rankings.
• New categories brought in significantly more visibility.
• Removing categories caused drops, but rankings recovered almost immediately once restored.

This aligns with previous studies by Sterling Sky and others.

 

[zackrobinson]

Wanted to share a study we did about category dilution. A common question we had from our customers is whether adding categories hurt my current ranking, or will adding new categories bring more traffic?

We did a study, you can find it here: Category Dilution Study

We have included the raw data and interactive graphs in the link above so you can check it out for yourself. In short, we found:

• No dilution: Adding relevant categories did not hurt existing rankings.
• More traffic: New categories brought in significantly more visibility.
• Fast recovery: Removing categories caused drops, but rankings recovered almost immediately once restored.

This aligns with previous studies by Sterling Sky and others.

Great study, thanks for sharing.


This matches what we’re seeing too — adding Relevant categories doesn’t hurt rankings and usually increases visibility. Issues tend to happen only when categories aren’t a good fit for the business.

 

[WilliamGMBE]

Oh yes, agree. Our sample size here is small, but the data is very clear about it.

We also see that some categories search ranking increased a lot when added, while some new categories added did make that much of the difference.

Like the graph below in the experiment, on phase 2 we added total of 9 categories, some categories search term increased in ranking while some didnt. Not sure why, maybe website data.

 

[JS Girard]

Oh yes, agree. Our sample size here is small, but the data is very clear about it.

We also see that some categories search ranking increased a lot when added, while some new categories added did make that much of the difference.

Like the graph below in the experiment, on phase 2 we added total of 9 categories, some categories search term increased in ranking while some didnt. Not sure why, maybe website data.

Though website data is also a very possible culprit, I'd like to offer another possible factor.

I think it also depends on whether the algorithm already associates the keyword with the main category or not.

Not a tested example, just to explain: if you take a keyword like "AC unit repair", that keyword might very well be equally associated with the "HVAC contractor" and "Air conditioning repair service" categories, so adding one when the other is already present wouldn't make much of a different compared to a case where the main category was "Air duct cleaning service".

That theory is based from my past experience seeing keyword clearly shift during algorithm updates between categories or from no strong association to being associated with a category.

 

[WilliamGMBE]

Though website data is also a very possible culprit, I'd like to offer another possible factor.

I think it also depends on whether the algorithm already associates the keyword with the main category or not.

Not a tested example, just to explain: if you take a keyword like "AC unit repair", that keyword might very well be equally associated with the "HVAC contractor" and "Air conditioning repair service" categories, so adding one when the other is already present wouldn't make much of a different compared to a case where the main category was "Air duct cleaning service".

That theory is based from my past experience seeing keyword clearly shift during algorithm updates between categories or from no strong association to being associated with a category.

That is an interesting point. Can see how that could be another possible reason.