Setting the existing-customer cap to 20% added 41% new buyers

Setting the existing-customer cap to 20% added 41% new buyers
Fashion retailer, Advantage+ Shopping, 45d, $160k spend.

Advantage+ Shopping has an existing-customer budget cap (max share of spend allowed to go to current customers). Left at default, it was running near 55%.

Forcing it to 20%:
— Headline ROAS: 3.4x → 2.9x ▼0.5
— New customers: +41% ▲
— New-customer CPA: $36 → $33 ▼

The lower headline number reflected real incremental growth instead of recycled retention.

Read: the existing-customer cap is the single most under-used lever in Advantage+. Set it on purpose.