Jan 6, 2024 · 22m · y-combinator
Consumer Startup Metrics | Startup School · Y Combinator
0:00 / 0:00
▶ Watch on YouTube →
gold bands on the timeline = statements, start to end. Hover to read, click to jump. CC turns on captions
In this Y Combinator Startup School lecture, former Monzo co-founder Tom Blomfield presents key performance metrics for consumer startups, covering user growth targets, organic virality, unit economics, retention dynamics, and Net Promoter Score. He provides actionable benchmarks and insights to help founders build sustainable, product-led consumer ventures.
How this conversation actually went
Every chapter scored 0–10 on four independent dynamics. Hover any point for the reasoning behind the score. How this is scored →
The partners as informed peer 0.0 Guest teaching 0.0 Guest disagreement 0.0 The partners pushing back 0.0
speaking balance: gold is the partners, purple is the guest (3 minute bins)
Sharpest disagreement ▶ 9:30 Critique of Paid Ad Platform Dependency
Tom Blomfield strongly warns against relying on Google and Meta ad bidding wars that erode margins to zero.
Hardest push from the partners ▶ 7:00 Dismissal of Complex Multi-Touch AttributionBlomfield dismisses convoluted multi-touch attribution models as unnecessary hassle compared to simple UTM tags and direct user questions.
Biggest teaching moment ▶ 13:00 Lesson on Scaling Negative Unit EconomicsBlomfield educates founders on the severe risk of scaling negative unit economics, citing Monzo burning capital at -40 pounds per user.
The partners hold their own ▶ 16:20 Pragmatism Over Precision in Magic MomentsBlomfield advises teams not to get pedantically bogged down in exact metric thresholds once a clear tipping point is identified.
the scores for every segment, with the reasoning behind each
| Chapter | Topic | The partners as informed peer | Guest teaching | Guest disagreement | The partners pushing back | Why |
|---|---|---|---|---|---|---|
| Monthly Growth Rate Benchmarks for Consumer Companies | 0 | 0 | 0 | 0 | Solo lecture format where Tom Blomfield establishes consumer growth rate benchmarks and the difference between virality and network effects. There is no host interaction. | |
| Designing Shareable Moments and Multiplayer Features | 0 | 0 | 0 | 0 | Blomfield details designing shareable loops and shifting products from single-player to multiplayer experiences. Monologue presentation without host counterpoints. | |
| Paid Acquisition Channels and Customer Acquisition Cost (CAC) | 0 | 0 | 0 | 0 | Blomfield explains paid acquisition channel tracking and calculating true customer acquisition cost down to active, monetized users. Solo instructional delivery. | |
| Organic vs. Paid Split and Ad Platform Pitfalls | 0 | 0 | 0 | 0 | Blomfield warns founders against over-relying on major ad platforms due to bidding dynamics driving margins to zero. Pure monologue lecture. | |
| Unit Economics and Variable Cost Optimization | 0 | 0 | 0 | 0 | Blomfield defines unit economics and isolates variable costs using early Monzo examples. Delivered as an uninterrupted educational segment. | |
| Measuring Retention and Identifying the Magic Moment | 0 | 0 | 0 | 0 | Blomfield explores identifying the 'magic moment' that drives long-term retention and onboarding redesigns. Monologue presentation. | |
| Net Promoter Score (NPS) Mechanics and Optimization | 0 | 0 | 0 | 0 | Blomfield outlines Net Promoter Score mechanics, benchmarking +50 for consumer startups, and cautioning against altering measurement methods. Solo presentation. | |
| Summary Recap and Final Benchmarking Advice | 0 | 0 | 0 | 0 | Blomfield recaps the core consumer metric benchmarks and reminds founders to contextualize rules for their specific industry. Concluding monologue. |
Statements from this episode (15)
Blomfield: Monzo has grown to about eight million UK customers
“I was previously the founder of a consumer online bank called Monzo. It's now up to about eight million customers in the UK.”
Blomfield: 5% monthly growth is unlikely to yield breakout consumer success
“A good growth rate is 15% month over month. At that rate, you'll five X your user base every year. 10% monthly growth for consumer company is okay. It means you'll approximately triple your user base every year. Five percent a month or lower is unlikely to rea…”
Blomfield: Monzo Reached 1M Customers Before Spending on Direct Marketing
“We got to a million customers at Monzo before we spent any money on direct marketing or advertising.”
Blomfield: Paid referral schemes are paid acquisition, not organic virality
“I would treat this as paid acquisition, actually. You're spending money to acquire customers, and if you stop spending, those customers won't appear.”
A friend gamed Zipcar's referral scheme via Google Ads for a year
“So I had a friend who in the early days of Zipcar just set up a bunch of cheap Google ads that bid on Zipcar and then would redirect them straight to Zipcar and milk the referral scheme. And so he drove free Zipcars for a year and then got banned for life from…”
Blomfield: Complex multi-touch attribution is more hassle than it is worth for startups
“You can get really convoluted with, you know, first touch attribution, last touch, multi-touch attribution. It's often, ah, way more hassle than it's worth. Simply using those UTM referrers or asking your customers where they came, where they heard about your …”
Blomfield: Monzo killed a cheap acquisition channel due to negative customer LTV
“Back at Monzo, we found a particular money saving blog that was very, very cheap to get users from. They sent us hundreds and hundreds of users when we were eventually paying for advertising. It seemed very, very cheap, but the customers, it turns out, were de…”
Blomfield: Top consumer startups get over 80% of growth organically
“The best consumer companies have a split of organic versus paid growth of something like north of 80% organic to 20% paid.”
Blomfield: Over-relying on Google and Meta ads pushes startup margins to zero
“You all take your margins to zero and Google and Meta end up making all the money. That's why it's so dangerous to be so reliant on paid growth.”
Monzo scaled to 500k users with unit economics of -£30 to -£40
“In the early days of Monzo, we were at -30 or -40 pounds per customer per year, and we scaled to half a million customers before we fixed them.”
Monzo defined active retention as at least one transaction per week
“So for Monzo, we chose one transaction, at least one financial transaction every week.”
Adding three friends at sign-up boosted Monzo retention by 20%
“Because we had a bank account, but also this Venmo-like functionality built into the product where you could send and receive money, customers who added three friends from their phone book to their Monzo account so they could send and receive money, as they si…”
Blomfield: Startups should not obsess over exact definitions of retention magic moments
“Simply finding that kind of tipping point that looks about right from your metrics, and then agreeing with everyone that that's what you're going to optimize for, rather than being really pedantic about the exact definition is probably the best way to go.”
Blomfield: A +50 NPS is the minimum baseline for new consumer companies
“If your net promoter score, your MPS, is not extremely high as a new consumer company, you're toast. You pretty much have to re-engineer the product to make it something that people love. The reason is it correlates extremely well with word of mouth referral. …”