Post-Purchase Survey for Google Ads on Shopify

Asking customers how they discovered your brand after buying. Here's how this applies specifically to Google Ads advertising and why causal inference gives you a clearer picture than Google Ads's own reporting.

What is Post-Purchase Survey?

Asking customers how they discovered your brand after buying. For Shopify brands running Google Ads campaigns, understanding this concept is critical because it directly impacts how you evaluate Google Ads's contribution to your revenue.

Post-Purchase Survey	Google Ads reports	Causal truth
Data source	Google Ads Ads Manager	GA4 + Shopify (independent)
Methodology	Click/view tracking	Causal inference
Bias	Self-serving (overcredits Google Ads)	Independent (no platform bias)

Why Google Ads's view of post-purchase survey is misleading

Branded search captures existing demand — customers who would've bought anyway get attributed to Google
Google's data-driven attribution model is a black box that still favors Google channels
Last-click attribution gives Google 100% credit when it's the final touch — ignoring discovery channels

How causal inference measures post-purchase survey for Google Ads

Separates branded search (demand capture) from non-branded (demand creation) — see true incremental ROAS
Causal inference measures what would've happened WITHOUT Google Ads — the real test of value
Cross-channel Shapley values show Google's true contribution alongside Meta, TikTok, and email