What paid audience overlap with existing customers costs you
The short answer
Upload your active customer list to each ad platform and match it against your acquisition audiences to size the paid audience overlap with existing customers. The match shows how many acquisition impressions go to people who already buy from you. Multiply their share of impressions by your acquisition budget to estimate the waste.
Why it matters
Every acquisition dollar spent on an existing customer buys a sale you might have had anyway, often with a new-customer discount attached. Sizing the overlap gives leadership a clear figure for wasted media and the case for a suppression list.
The question to ask
Copy this into Lexi as written.
What the answer looks like
Illustrative output on sample data
Illustrative example: how Lexi answers this for a sporting goods retailer. It matches 280,000 customers active in the past 24 months against one quarter of paid prospecting audiences.
- Existing customers reached by acquisition ads: about 61,000
- Share of prospecting impressions: 14%
- New-customer code used by existing customers: 2,300
What the data shows
About $126,000 of a $900,000 quarterly prospecting budget reached people already buying.
What it means
Some of those existing customers then used a code meant for new customers.
What to do
Suppress active customers from prospecting and restrict the new-customer code to first orders.
Matching uses hashed email and phone, so some overlap will go unseen. Want me to push a suppression list to Meta and Google Ads?
Frequently asked questions
What is paid media wastage on existing customers?
It is acquisition spend that reaches people who already buy from you. Those impressions and clicks are meant to find new customers, so any sale they produce is often one you would have made anyway, sometimes with a new-customer discount on top.
Why do platform reports miss the overlap?
Ad platforms report reach and conversions, but they do not know who your customers are unless you tell them. Store customers and people who use different emails online look like new prospects. Matching your full customer file, from every channel, is the only way to size the overlap.
Is sizing the overlap the same as building a customer suppression list?
They go together. Sizing the overlap shows how much acquisition spend reaches existing customers and builds the case for action. The suppression list is the fix: an exclusion audience uploaded to each platform so existing customers stop seeing acquisition ads.