Increase repeat purchases

Turn "only 12% buy again" into a ranked backlog. Leave the how-to and the papers in the Depth skills. Several effects show up in retention over years, not in next month's numbers — say so. Every number is what a cited study measured in its own context; do not turn it into a forecast for the user's repeat rate.

When to use

• The user names repeat rate, retention, lifetime value, or "second order" as the goal
• Reviewing what happens after checkout: emails, box contents, returns, loyalty

When not to use

• First purchase → increase-conversion; order size → increase-aov
• Cart and payment-step UX → checkout-ux; abandonment email timing stays here via post-purchase
• Review solicitation and complaint handling in depth → reviews; referral mechanics → referrals

Inputs

Collect, or state your assumption:

• Product and how long it takes to judge (instant vs weeks)
• Post-purchase emails: what is sent, when, first question asked
• Box contents (inserts, codes, packaging)
• Return and refund policy; loyalty program (opt-in or automatic, tiers, reward type)
• Abandoned-cart email timing; whether the store replies to reviews

Procedure

Walk each check; include applicable levers the user didn't mention; list the rest as considered.

1. Loyalty: automatic, single tier, threshold reward. Enroll everyone; one rule ("buy 10, get 1 at no cost"). Effect is in multi-year retention. Depth: post-purchase.
2. Feedback request with a positive open-ended first question. "What did you enjoy most?" before any rating. Depth: reviews.
3. Ask for reviews at 9–13 days, later for products that take weeks to judge. Measured on review volume, not repeat purchase; it is the delivery vehicle for step 2. Depth: reviews.
4. Handwritten thank-you note, nothing attached. A discount on the note cancels the effect. Depth: post-purchase.
5. Instant refund when the return ships. Carrier scan, not after inspection, for items that don't need inspection. Depth: post-purchase.
6. Free, easy returns. Depth: post-purchase.
7. Free-shipping membership with a minimum order. Depth: post-purchase.
8. Reply to every review — measured on ratings and volume, not repeat. Depth: reviews.
9. Abandoned-cart reminder at 24–72 h, never within the hour. Depth: post-purchase.
10. Referrals as the next step once repeat customers exist: friend's benefit as the headline. Depth: referrals.
11. Rank. Note which effects are long-horizon (loyalty) versus immediate (email timing, refund timing). Cheap changes ahead of program builds at equal effect.

Output

Then: what already complies. Each effect was measured on its own; don't add them up. Ship the top two or three, measure, then take the next.

Common mistakes

• Inventing a lift ("could double repeat rate") — quote the study's number and its context.
• Building a replenishment sequence first — reasonable, but not in this evidence.
• Making the loyalty program visible but still opt-in — the finding is automatic enrollment.
• Keeping the discount on the thank-you note — it cancels the note's effect.
• Judging the loyalty program on next quarter's numbers — the effect is in multi-year retention.

Quick reference

Evidence and effect sizes: see reference.md.