SERP Overlap

SERP Overlap measures the percentage of shared results in the top 10 Google results for two different queries. When overlap exceeds 50%, Google views these queries as closely related, indicating clusters should be combined (MERGE). Below 30% indicates clearly different topics that require separate clusters.

The 30-50% range requires manual review for clustering decisions. SERP Overlap is a key metric in cluster validation, which is the fourth step of the clustering pipeline.

This metric differs from SERP Coherence (which measures coherence within a cluster), as SERP Overlap checks relationships between clusters. For example, 'inheritance law' and 'succession' may show 70% overlap, indicating these clusters should merge.

In practice, SERP Overlap is calculated by fetching the top 10 results for both queries and counting shared domains. If 6 out of 10 domains appear in both result sets, that's 60% overlap.