How much of a problem is audience overlap between Facebook ad sets?

Question

As context, I've heard very conflicting things around audience overlap

• Some folks (including people at FB) have said ad sets with overlapping audiences do not hurt performance.
• Others say ad sets competing against each other drive up CPMs and hurt performance.

My own experience has been that when I run distinct ad creatives in different ad sets with same targeting (for instance -> I might target a 1% lookalike in a certain country with two ad sets: one with display ads, and another with video ads) - I really havent seen any deterioration in performance. In some cases, I've run multiple ad sets targeting the same audience (portrait size ads tailored to IG stories, display ads, video ads & carousels) - and I still havent seen any performance deterioration.

What has people's experience been around audience overlap?

Answer 1

My experience running FB ads is the following : 

• when I ran LaL targeting adsets, it was key and mandatory to avoid any overlap between adset as the audience is not that large, especially in tier 1 non US country like western Europe. 
• For other targeting, i try to avoid big / obvious overlap. I can't confirm the potential CPM increase but from my perspective, this is more related to common sense to avoid them as much as possible.  

Answer 2

Audience overlap isn't really much of a concern on Facebook -- Facebook has 1.56BN DAUs as of Q1 2019 -- but it can become problematic when you start using very broad lookalike scoping (eg. 10%) on AEO and VO campaigns that are running simultaneously (see more in this answer: What is the difference between AEO and VO bid types on Facebook?).

VO and AEO campaigns naturally tend to iteratively reduce / hone targeting to the same groups of people, and running campaigns with those types of bid strategies on the same audiences will magnify the impact of the simultaneous targeting.

EDIT: re-reading this answer a few weeks after writing it, I think the point I was trying to make isn't clear.

Audience overlap doesn't have to be / shouldn't be a concern on Facebook: Facebook's penetration is large enough that, if you are smart about campaign construction, you don't need to be concerned with audiences overlapping (and thus driving up your CPMs).

But what does being smart about campaign construction mean?

• If you are running multiple AEO / VO campaigns, you are either targeting very specific segments that are independent of each other, or you are running fundamentally different creatives;
• You aren't using broad Looaklike (eg. 5%+) audiences in the same geos across multiple campaigns;
• You aren't running test campaigns against the same custom audiences as live campaigns with significant budgets;
• With multiple AEO / VO campaigns, you are using very strong signal events (eg. purchases) and not up-funnel events like registration or tutorial complete. If you have multiple event-optimized campaigns running, make sure the events are down-funnel enough to really segment users.

The point I was trying to make with the original post was that audience overlap doesn't have to be a real liability on Facebook -- it's certainly possible to avoid that problem with just a little bit of planning and strategy. Obviously if you are spinning up multiple VO campaigns with 10% LaL audiences based on payer seeds and targeting up-funnel events in the US, you'll run into problems with overlap.

Answer 3

I'm surprised to hear Facebook account managers would have say it's fine. They always insisted it's not, and overlap should be avoided at all costs. Their advice isn't necessarily representative of how the auction work anyway, so one has to figure out by himself.

I try to avoid important overlaps myself. I tolerate but a small % of audiences overlap, but not a large one, and not between many Adsets. Until 2018 changes I've seen accounts doing the opposite and seeing good results. I do believe Facebook is penalizing this more over time. Especially as you're running AEO/VO, but then as you bundle larger audiences, it's easier to have a clean split.

Answer 4

I've had a lot more experience with campaigns that are much more hyper-segmented. For example, I've run into issues with severe overlap when targeting limited populations like Puerto Rico or smaller states in the US.