How do you decide when to merge or split segments?

Merge segments when two groups behave nearly identically and treating them separately adds operational complexity without improving results. If your weekly and biweekly newsletter subscribers respond to the same content at similar rates, maintaining two workflows may not be worth the effort.

Split segments when you detect meaningful behavioral differences that suggest different messaging would perform better. If half your high value customers respond to discount offers while the other half prefers premium content, splitting lets you serve both effectively.

Use engagement metrics as your guide. Compare open rates, click rates, conversion rates, and unsubscribe rates between segments. If the differences are statistically significant and actionable, keep them separate. If the differences are marginal or inconsistent, consider merging.

Watch for segment overlap. When subscribers frequently qualify for multiple segments and receive redundant or conflicting messages, consolidation may simplify the experience. Conversely, when a large segment shows high internal variance in behavior, splitting can reveal hidden opportunities.

Review segment performance quarterly. Segments should earn their existence by delivering measurable value. If they don't, simplify the structure.