why Google utm source's conversions rate suddenly showed a very large increase

Topic summary

Sudden spike in Google-source CVR (conversion rate) beginning Aug 6, without a corresponding change in overall CVR or GMV (Gross Merchandise Value), raising concerns about data accuracy.

A screenshot is referenced and appears central to illustrating the trend.

Proposed cause: misconfigured UTM parameters—recent emails or campaigns may have used utm_source=Google instead of Email, inflating Google’s conversion rate via misattribution.

Implications: Channel attribution may be skewed; Google looks more effective while total performance remains stable, suggesting data labeling rather than real performance change.

Key terms: UTM source (URL tracking parameter indicating traffic origin), CVR (percentage of visitors converting), GMV (total sales value before returns/discounts).

Suggested actions:

  • Audit recent campaign links for correct UTM source/medium/tagging.
  • Review analytics reports (Shopify, GA4, Google Ads) for channel mapping and any tagging automation changes.
  • Compare email send dates with the CVR spike; check sessions, conversions, and assisted conversions by channel.

Status: Unresolved; awaiting confirmation of tagging or further data.

Summarized with AI on December 16. AI used: gpt-5.

hi,

Since Aug. 6th, we have a big increase on CVR of Google source, but not big change on overall CVR & GMV. Is something wrong with the data?

Best,

Is it possible that you sent out an email using the wrong UTM source? Google instead of Email?