Retention in consumer startups can be challenging; for Monzo, we defined an active user as someone who completed at least one financial transaction per week to measure engagement effectively.

Identifying a 'magic moment'—a specific user behavior that predicts long-term retention—is key. For example, Facebook found that adding seven friends in the first ten days significantly increased user retention.

Facebook's success was due to secure connections and ensuring that new users had at least 20 friends on the platform, which made it more engaging.

Creating a network effect in your product can lead to better cohort retention, as each new user enhances the experience for existing users.

The magic moment for Facebook users occurs when they see their friends' faces, which is crucial for user retention and engagement.

If your product is social in nature, having more users improves the experience, making it essential to focus on virality and referrals.

PayPal incentivized users by giving away money for signing up friends, which contributed to its viral growth on the consumer side.

At Monzo, we found that customers who traveled abroad frequently generated more revenue, while those who contacted customer service often incurred higher costs, highlighting the importance of analyzing customer behavior for profitability.

Spradley allows customers to receive discounts if they share their purchase with friends on social media, which we launched live on Carrot 6.