A good growth rate for consumer startups is 15% month-over-month, which allows the user base to 5x every year. A 10% monthly growth rate is acceptable, tripling the user base annually, while 5% or lower is unlikely to lead to breakout success.
Virality refers to users introducing the product to others through its use, such as sharing achievements on social media. Network effects occur when the product becomes more valuable as more people use it, like WhatsApp, where the ability to message more users increases its utility. Both are crucial for organic growth.
Organic growth, driven by virality and network effects, is sustainable because it doesn't rely on continuous ad spend. Once established, these mechanisms continue to attract users without additional costs, unlike paid growth, which requires ongoing investment and is vulnerable to platform changes and rising acquisition costs.
Paid referral schemes can lead to cannibalization, where users who would have referred others for free are now paid, and fraud, where individuals exploit the system for personal gain. Both issues can inflate acquisition costs and reduce the effectiveness of the referral program.
Consumer startups should measure CAC based on the cost to acquire an active, monetized, and retaining user, not just a sign-up. This ensures that the cost reflects the value of users who contribute to long-term profitability, rather than those who may churn quickly.
Unit economics measure the revenue generated per customer minus the variable costs associated with serving them. It is crucial for understanding profitability on a per-customer basis and optimizing costs and revenue streams before scaling the user base.
A 'magic moment' is a user behavior or activity that predicts long-term retention, such as adding friends on Facebook or booking a stay on Airbnb. Identifying and optimizing for this moment during onboarding can significantly improve user retention and satisfaction.
A consumer startup should aim for a minimum Net Promoter Score (NPS) of +50. This score indicates strong customer satisfaction and likelihood of word-of-mouth referrals, which are critical for organic growth and long-term success.
In this episode of Startup School, YC Partner Tom Blomfield dives deeper into the metrics that matter most for consumer startups. Tom discusses paid and organic user growth, unit economics, net promoter scores, and the "magic moment" in your product that is most important to track.