How To Improve Cohort Retention with David Lieb | Startup School

The Foundation of Startup Success

At Y Combinator, there's a famously simple motto that guides everything: make something people want. But here's what gets talked about much less - how do you actually know if you've accomplished this goal?

The Critical Gap Most Founders Miss:

1. The Question Everyone Asks - Did we make something people want?
2. The Problem Most Face - No clear, quantitative way to answer this question
3. The Solution That Changes Everything - Cohort retention analysis

Why This Matters More Than You Think:

• Most founders give handwavy answers when asked about user retention
• Without proper measurement, you're flying blind on product-market fit
• The difference between guessing and knowing can make or break your startup

"I remember one specific moment I was pitching a very prestigious VC firm for our Series A and they asked me 'hey Dave, how's your cohort retention?' and I gave them a very handwavy answer and then after the meeting I went on my computer and I googled cohort retention and I realized that what I said must have made absolutely no sense." - David Lieb

The Track Record Behind This Advice:

• Bump: One of the first mobile apps to reach 100+ million users
• Google Photos: Formed the basis for the product serving over 1 billion users today
• Hard-Won Lessons: Learned the very hard way how to know when you have NOT yet made something people want

Timestamp: [0:01-2:31]

The Single Best Metric for Product-Market Fit

Cohort retention is the idea of tracking what fraction of your new users keep using your product over time. But it's not just another analytics metric - it's fundamentally different from how most founders think about measuring success.

The Key Breakthrough Insight:

Track individual groups of new users (cohorts) over time instead of looking at your entire user base mixed together.

Why This Approach Is Revolutionary:

1. Individual User Journey Clarity - See how specific groups of users actually behave over time
2. Better Pattern Recognition - Identify trends that get hidden in aggregate data
3. Actionable Intelligence - Make decisions based on real user behavior, not vanity metrics

The Three Critical Components You Must Define:

1. How to Isolate Cohorts

• Most common: Group by when they first used your product (weekly/monthly)
• Advanced: Slice by country, acquisition channel, device, or customer characteristics

2. What Action Counts as "Active"

• Simple approach: Did they open the app or visit the site?
• Better approach: Pick a specific feature that correlates with real value

3. Which Time Period to Measure

• Must match your product's intended usage pattern
• Daily for social/entertainment apps
• Weekly for utility products
• Quarterly/annually for infrequent-use products like travel

Timestamp: [2:31-3:58]

The Make-or-Break Decision That Most Founders Get Wrong

The action you choose to define an "active user" is absolutely critical - it determines whether your retention metrics actually reflect real value delivery or just superficial engagement.

Real Examples from Billion-User Products:

Instagram's Approach:

• Action: Viewed three or more posts
• Reasoning: Filters out users who open the app but don't engage with content
• Why Three: Sometimes people open Instagram, don't touch the screen, get no value, and immediately leave

Uber's Method:

• Action: Completed a ride
• Focus: Actually took a ride and ended up at a destination
• Value Connection: Direct correlation with receiving the core service

Google Photos Strategy:

• Action: Tapped and viewed a photo full screen
• Logic: Whether viewing your own photos or shared photos, full-screen viewing indicates real value extraction
• Insight: This behavior shows genuine engagement with the core product value

The Golden Rule for Action Selection:

"The best action to pick is one that is really correlated with the user getting real value from your product and you want to try to filter away things where a user might be touching your product in some way but not getting real value." - David Lieb

Key Principles to Follow:

1. Value Correlation - Choose actions that directly relate to your product's core value proposition
2. Filter Noise - Eliminate superficial interactions that don't indicate real engagement
3. Specific Over General - Pick precise behaviors rather than broad activities like "opened app"
4. Test and Refine - Your chosen action should evolve as you better understand user value patterns

Timestamp: [3:58-5:35]

Matching Measurement Frequency to User Intent

The time granularity you choose for measuring cohort retention must align with how you actually intend users to engage with your product. Get this wrong, and your metrics become meaningless.

Time Period Selection by Product Category:

Daily Measurement (Social & Entertainment):

• Examples: Instagram, TikTok, YouTube
• Rationale: These products are designed for daily consumption
• User Expectation: Daily engagement is the intended behavior
• Measurement: Track if users perform your chosen action each day

Weekly Measurement (Utility Products):

• Examples: Google Photos, Uber
• Logic: Users don't necessarily need these every single day
• Natural Usage: Sporadic but regular engagement
• Measurement: Track if users are active within each week

Quarterly/Annual Measurement (Infrequent Use):

• Examples: Airbnb, travel apps
• Reality Check: People don't travel 3-4+ times per year
• Appropriate Scale: Match the natural usage frequency
• Measurement: Track engagement over longer periods

The Critical Matching Principle:

Why This Matters:

1. Accurate Insights - Mismatched time periods create false signals about user engagement
2. Proper Expectations - Your measurement should reflect realistic user behavior
3. Actionable Data - Correct time granularity leads to meaningful optimization opportunities

Common Mistakes to Avoid:

• Using daily measurement for products meant for weekly use
• Applying weekly metrics to daily-use products
• Ignoring your product's natural usage rhythm

The Key Question to Ask:

"What time period matches what we intend for our product?"

This alignment between measurement and intention is fundamental to getting retention insights that actually help you build a better product.

Timestamp: [5:35-6:48]

The Practical Mechanics of Measuring Cohort Retention

Now let's dive into the actual measurement process using a real example. The triangle chart is the foundational tool that makes cohort retention analysis both visual and actionable.

Understanding the Triangle Chart Structure:

The Rows (Cohorts):

• Each row represents all new users from a specific month
• January cohort: 12 new users
• February cohort: 27 new users
• Each subsequent month adds a new row

The Columns (Time Progression):

• Track each cohort's behavior in every subsequent month
• First column: Initial cohort size (always 100%)
• Each column to the right: Performance in later months

Real Example Walkthrough:

January Cohort Journey:

1. Month 1 (January): 12 new users join
2. Month 2 (February): 6 of those 12 users return
3. Month 3 (March): 4 of the original 12 users are active
4. Month 4 (April): 5 of the original 12 users return

Key Insight - Numbers Can Fluctuate:

• Users can return after being inactive (4 → 5 in the example above)
• Each user counts only once per time period, regardless of usage frequency
• The number can never exceed the original cohort size

The Party Analogy That Makes It Click:

"I like to think about this as a party. Say you're having a party, you've got your room. When people come into the room you kind of tag them, you give them like a little sticker that says what month they came to your party in." - David Lieb

How the Party System Works:

• January stickers for all users who joined in January
• February stickers for all users who joined in February
• Each month, count how many people with each sticker are still at your party

The Diagonal Line Insight:

The highlighted diagonal represents one real calendar month, showing you:

• Where all active users in December originally came from
• Which cohorts contributed to that month's total activity
• The composition of your active user base at any point in time

Timestamp: [6:48-9:11]

From Data Points to Strategic Understanding

The raw numbers in your triangle chart are just the beginning. The real power comes from converting these into percentages and visualizing trends that reveal the health of your product.

The Percentage Transformation:

Why Percentages Matter:

• Normalization: Compare cohorts of different sizes fairly
• Trend Recognition: See patterns across different time periods
• Standardized Measurement: First column always shows 100% by definition

What the Percentages Reveal:

1. Horizontal Analysis (Across Rows): How each individual cohort performs over time
2. Vertical Analysis (Down Columns): Whether you're improving with each new cohort
3. Overall Trends: General direction of product-market fit

The Power of Line Graph Visualization:

Why Line Graphs Beat Tables:

• Pattern Recognition: Immediately see retention curve shapes
• Cohort Comparison: Overlay multiple cohorts to spot improvements
• Time Series Analysis: Track how your product evolution affects retention

What Each Line Represents:

• Individual Cohort Journey: One line = one group of users over time
• Data Density: Older cohorts have more data points (11 months for January)
• Recent Cohorts: Newer cohorts show early indicators (November/December with 2-3 data points)

Key Questions This Visualization Answers:

Product Health Indicators:

1. Are retention curves improving over time? (Compare line positions)
2. Where do users typically drop off? (Look for steep declines)
3. Do we have a stable retention floor? (Where lines level off)
4. Are recent product changes working? (Compare newest cohort lines)

Strategic Decision Points:

• Cohort Quality: Are newer user groups stickier than older ones?
• Product Iteration Impact: Do retention curves improve after major updates?
• Time to Value: How quickly do users establish sustained usage patterns?

This transformation from raw data to visual insights is where cohort retention becomes a powerful strategic tool rather than just another metric.

Timestamp: [9:11-10:27]

Essential Insights:

1. Cohort retention is the single best quantitative way to know if you've made something people want - It tracks individual groups of users over time rather than mixing your entire user base together
2. The action you choose to define "active users" makes or breaks your analysis - Pick something that correlates with real value delivery, not just superficial product interaction
3. Your measurement time period must match your product's intended usage pattern - Daily for social apps, weekly for utilities, quarterly for travel - misalignment creates meaningless metrics

Actionable Insights:

• Start with monthly cohorts and weekly measurement if you're unsure about your product's natural rhythm
• Choose an action that filters out users who touch your product but don't get real value from it
• Use the triangle chart method to visualize both individual cohort performance and overall improvement trends
• Convert raw numbers to percentages and line graphs to spot patterns that drive strategic decisions

Timestamp: [0:01-10:27]

People Mentioned:

• David Lieb - YC Group Partner, former founder of Bump and Google Photos team member, sharing insights from building products used by over 1 billion people

Companies & Products:

• Y Combinator - Startup accelerator with the motto "make something people want"
• Bump - Contact sharing app that reached 100+ million users before being acquired by Google
• Google Photos - Photo management service serving over 1 billion users, based on technology from Bump acquisition
• Instagram - Example of daily-use social platform with retention measurement strategy
• Uber - Example of utility product measuring completed rides as active usage
• Airbnb - Example of infrequent-use product requiring quarterly/annual retention measurement
• TikTok - Referenced as daily-use entertainment platform
• YouTube - Referenced as daily-use entertainment platform

Concepts & Frameworks:

• Cohort Retention Analysis - Method for tracking groups of new users over time to measure product-market fit
• Triangle Chart - Visualization tool showing cohort performance across time periods
• Active User Definition - Strategic choice of actions that correlate with real value delivery
• Time Period Alignment - Matching measurement frequency to intended product usage patterns

Timestamp: [0:01-10:27]

The Counter-Intuitive Truth About Successful Products

Looking at two products side by side, it's easy to think the one with higher initial retention is automatically better. But this assumption can lead you completely astray when evaluating product-market fit.

The Tale of Two Products:

Product A (Black Line):

• Initial Performance: Retains way more users in first month or two
• Looks Great Early: Numbers stay well above 50%
• The Hidden Problem: Curve keeps declining toward zero
• Long-term Reality: Will eventually churn all users

Product B (Orange Line):

• Rough Start: Loses more than half its users quickly
• Low Absolute Numbers: Drops to maybe 20% of initial cohort
• The Magic Moment: Curve becomes stable and flat
• Strategic Advantage: Stops losing users entirely

The Only Thing That Actually Matters:

"The only thing that matters and I can't stress this enough, the only, only thing that matters is whether your cohort curves get flat. The shape of the curve is what matters, not the absolute number." - David Lieb

Why Flatness Trumps Height:

1. User Accumulation: Flat curves let you accumulate users over time
2. Escape the Treadmill: Without flatness, you're constantly replacing churned users
3. Long-term Growth: Even small retained percentages compound into massive user bases
4. Sustainable Business: Flat retention gives you a foundation to build on

The Real-World Validation:

• Google Photos Reality: 80% of users left pretty immediately
• The Key Insight: 20% stayed and used it every week "basically forever"
• Confidence Gained: Within 6 weeks of launch, David was certain they'd reach 20% of all humans
• The Outcome: 4+ years later, well over a billion users (approaching two billion)

"If your curves don't flatten out, I would say it's a pretty good sign that you haven't yet made something people want." - David Lieb

Timestamp: [10:30-14:02]

The Dangerous Self-Deception Traps Every Founder Falls Into

Even experienced founders make critical mistakes when measuring cohort retention. These aren't just errors - they're unconscious psychological defenses against disappointing data.

Mistake #1: Picking Too Large a Time Period

The Temptation:

• Quarterly or half-year measurements make everyone look better
• Larger time periods = higher retention by definition
• Who doesn't want better numbers for investors and employees?

The Bump.com Case Study:

"At Bump, this was a mistake I made. We would look at our weekly cohort retention curves because we thought that weekly was kind of the right period of time that users should be using Bump, and they were really bad." - David Lieb

The Dangerous Progression:

1. Week 1: Weekly retention looked terrible
2. Week 2: "Let's try monthly for investor meetings" (looked better)
3. Week 3: "Quarterly actually makes sense" (looked great!)
4. Reality Check: Bump wasn't designed for quarterly use - they were deluding themselves

The Unconscious Brain Factor:

"This is something to be consciously aware of and also realize that your unconscious brain is going to push you to widen your cohorts even though you probably shouldn't." - David Lieb

Mistake #2: Picking Too Easy an Action

The Notification Bell Trap:

• Using alerts to artificially drive "engagement"
• Users arrive but leave immediately without getting value
• Metrics look good but represent no real product usage

The Google+ Horror Story:

"There was a point in time, I kid you not, that the active usage of Google+ was determined by whether a user saw in the top right corner of every Google product a little notification bell that would have a red notification." - David Lieb

What Actually Happened:

• People were in Gmail, clicked the red bell to see what it was
• Got counted as "active Google+ users"
• Numbers looked amazing, but it was completely false
• These weren't active users - they were accidental clicks

Mistake #3: Using Payment as the Only Metric

The Counter-Intuitive Truth:

"Users first stop using your product and then they stop paying you for your product." - David Lieb

The Netflix Reality Check:

• You might not have watched Netflix in over a month
• But you probably haven't canceled your subscription
• Payment lags actual product usage by weeks or months

Better Approach:

Combine payment status WITH actual product usage: "Is paying AND actually used some part of my product this month"

Timestamp: [14:02-18:14]

The Simple Test That Cuts Through All the Confusion

Choosing the right action to measure is critical, but most founders overthink it. There's actually a straightforward way to nail this decision every time.

The Ultimate Rubric for Action Selection:

"Imagine you're sitting next to one of your customers. They're here at the table using your product. When you watch them use your product, what is the thing that's going through your head that helps you answer the question of whether that user is a good user of your product, that they're actually using it in the way that you intend? Whatever that answer is, I would recommend using that as the action in your cohort retention curves." - David Lieb

The Power of This Approach:

1. Intuitive Validation: Based on real user observation, not abstract metrics
2. Value Alignment: Captures behavior that correlates with your intended use case
3. Gut Check Integration: Uses your founder instinct about user success
4. Practical Application: Translates directly into measurable actions

Questions to Ask Yourself:

• What behavior makes you think "Yes, this person gets it!"?
• What action indicates they're using the product as intended?
• What would you be excited to see a user doing?
• What behavior correlates with them getting real value?

Avoiding the Single Point Trap:

The Daily Founder Mistake:

"I might have a founder who comes to me and says 'Dave, we're doing great, we have 80% week-over-week retention.' I scratch my head for a little bit and then I ask 'which week? What is the 80%? What's the numerator and what's the denominator in that number?' And almost always the founder doesn't know the answer to that question." - David Lieb

Why Single Points Mislead:

• Product A might have 75% week-three retention (sounds amazing!)
• But what about week two? Week four? The trend line?
• Without the full curve shape, you're flying blind
• Focus on curve shape, not individual data points

The Right Questions to Ask:

• What does the entire retention curve look like?
• Is the trend line flat, declining, or improving?
• What's the pattern across multiple time periods?
• Are you looking at shape or just cherry-picking good numbers?

Timestamp: [18:14-19:42]

The Hidden Dangers of Pre-Built Retention Dashboards

Those beautiful retention graphs in your analytics tools might be lying to you. Even worse, you might not even know what they're actually measuring.

The Analytics Tool Problem:

What Looks Good on the Surface:

• Every analytics suite has built-in cohort retention graphs
• They're convenient and seem professional
• The numbers often look encouraging

The Hidden Issues:

"Often those graphs aren't measuring exactly what you think they are. I've seen cases where these tools aren't separating cohorts in the way that the founders think they are." - David Lieb

Common Measurement Errors:

1. Rolling Retention vs. Cohort Separation: Mixing timeframes instead of pure cohort tracking
2. Cumulative vs. Period-Specific: "Has returned by date X" vs. "returned during this specific period"
3. Action Definition Mismatches: Tool's definition of "active" doesn't match your intention
4. Time Period Confusion: Weekly/monthly boundaries handled differently than expected

The Founder Knowledge Gap:

"Too many times founders come to me and show me their dashboard and I ask any questions about what those numbers actually represent and they don't actually know." - David Lieb

The Dangerous Pattern:

• Founders rely on pre-built dashboards
• Can't explain what the numbers actually mean
• Make strategic decisions based on misunderstood data
• Discover the truth too late in their journey

The Recommended Solution:

Build Your Own First:

"What I would recommend for most founders is to actually build these cohort retention curves on your own using your logs via a script or in Google Sheets. Do that a little bit upfront yourself to develop your own intuition about what's going on and how these are actually measured."

The Validation Process:

1. Manual Construction: Build curves yourself using logs or Google Sheets
2. Intuition Development: Understand exactly how the math works
3. Tool Comparison: Compare your manual version to analytics tools
4. Confidence Check: Only use tools when they exactly match your manual calculations

Monitoring Frequency:

• Not Multiple Times Daily: Don't obsess over real-time changes
• Not Even Daily: Cohort trends take time to develop
• Weekly or Bi-Weekly: Refresh graphs regularly to catch problems early
• Early Detection: When things go south, you want to know quickly

Timestamp: [19:42-21:26]

Essential Insights:

1. The only thing that matters is whether your cohort curves get flat, not the absolute retention percentage - A product that retains 20% forever beats one that starts at 80% but declines to zero
2. Your unconscious brain will push you to manipulate metrics to look better - Founders naturally gravitate toward larger time periods, easier actions, and cherry-picked data points that hide problems
3. Most analytics tools don't measure what you think they measure - Build your own cohort retention curves first to develop intuition before trusting any dashboard

Actionable Insights:

• Use the "sitting next to your customer" test to choose the right active user action - whatever makes you think "this person gets it" is your metric
• Build cohort retention curves manually in Google Sheets before relying on analytics tools to ensure you understand what you're measuring
• Focus on the shape of the entire retention curve rather than celebrating individual high-retention time periods
• Check retention curves weekly or bi-weekly, not daily, to catch problems early without obsessing over noise

Timestamp: [10:30-21:26]

Companies & Products:

• Google Photos - Real example where 80% of users left immediately but 20% stayed forever, leading to over 1 billion users
• Bump - Case study of founders manipulating time periods from weekly to quarterly retention to hide poor metrics
• Google+ - Example of misleading "active user" metrics based on accidental notification clicks rather than real engagement
• Netflix - Used to illustrate how payment lags actual product usage - users stop watching before they cancel subscriptions
• Google Sheets - Recommended tool for manually building cohort retention curves to develop understanding

Concepts & Frameworks:

• Curve Flatness Priority - The principle that retention curve shape matters more than absolute retention percentages
• Unconscious Metric Manipulation - The psychological tendency for founders to adjust measurements to show better results
• Rolling Retention vs. Cohort Separation - Different measurement methodologies that can lead to misleading results in analytics tools
• Customer Observation Test - The method of choosing active user actions based on real user behavior that indicates value delivery
• Manual Curve Construction - Building retention analysis from raw data before trusting pre-built analytics tools

Timestamp: [10:30-21:26]

The Strategic Levers That Actually Move the Needle

When your cohort retention curves aren't flat, you have five main approaches to fix the problem. Each targets a different aspect of the user experience and can dramatically improve your results.

Method 1: Improve Your Product

Core Product Enhancements:

• New Use Cases: Maybe it should do something completely different
• Performance Improvements: Speed up your product or reduce latency
• User Experience: Make the flows much simpler and more intuitive
• Feature Development: Add functionality that increases stickiness

What Success Looks Like:

You'll see cohorts get flatter AND flatten at higher levels. In practice, this might look like:

• Oldest cohorts: Poor performance, trending toward zero
• Middle period (June/July): Slight improvement, higher and flatter curves
• Recent cohorts (October/November): Flattening out much more and much sooner

Method 2: Acquire Better Users

The Target Mismatch Problem:

"You've built a great product but you're targeting it to the wrong type of customer." - David Lieb

Google Photos Gen Z Case Study:

• The Initiative: Marketing executive decided Google needed to target young people
• The Execution: Big push on Gen Z advertising and marketing
• The Results: Successfully brought in many young users
• The Problem: Those cohorts had really bad retention

Why the Mismatch Occurred:

"Google Photos is a tool to accumulate your life's memories and reminisce and if you're a young person, you don't have that many life memories yet and if you do, you probably aren't thinking much about reminiscing on that moment two years ago." - David Lieb

The Solution Approach:

Often improving user acquisition targeting is the easiest way to improve cohort performance.

Method 3: Slice and Analyze Your Cohorts

The Diagnostic Technique:

When cohorts aren't getting flat, immediately slice them by different dimensions:

• Geographic: By country or region
• Business Type: Big companies vs. small companies for B2B tools
• Device Type: Mobile vs. desktop users
• Acquisition Channel: Organic vs. paid vs. referral

What You'll Discover:

• Some cohort slices are very flat and perform really well
• Others are really, really poor
• This gives you clues about where to focus improvement efforts

Timestamp: [21:28-24:40]

The Two Most Overlooked Retention Multipliers

Beyond product improvements and better targeting, two specific strategies can dramatically improve cohort retention - and founders consistently underestimate their impact.

Method 4: Improve First User Experience & Onboarding

The Overlooked Opportunity:

"This is a thing again I think people overlook - they immediately jump to what the product does but often you just need to help your users get into a good state and be able to use your product in the right way." - David Lieb

Common B2B Tool Pattern:

• High Investment: Teams spend massive time building the tool itself
• Low Investment: Minimal thought about teaching people to use it
• Missing Elements: How to integrate into existing workflows

Critical Questions to Address:

1. Pre-State Analysis: What were they doing yesterday before they used your product?
2. Transition Planning: What do you want them to change about their life today?
3. Workflow Integration: How does this fit into their existing process?
4. Activation Strategy: How do you get them into a good state quickly?

The ROI Reality:

"Investing in this often is like the cheapest and easiest way to improve your performance of your cohorts." - David Lieb

Method 5: Build Network Effects Into Your Product

The Compounding Advantage:

Products where every subsequent user makes the product better for existing users create self-reinforcing retention improvements.

Network Effect Categories:

• Social Networks: More friends = more engaging content
• Sharing Networks: More people = more content to consume
• Communication Apps: More users = more utility for everyone
• Marketplace Dynamics: More buyers attract more sellers (and vice versa)

The Growth Dynamic:

"If you have a dynamic like that where the more people who use it the better it gets, you should see cohort improvement over time as that network grows and becomes more dense." - David Lieb

Strategic Focus Areas:

• Dense Network Building: Focus on creating good, dense networks around existing users
• Quality Over Quantity: Better to have smaller, highly engaged networks than large, sparse ones
• Network Density: Look for ways to increase connections between users
• Value Amplification: Each new user should meaningfully improve the experience for others

The Measurement Benefit:

With strong network effects, you should see automatic cohort improvements over time without other interventions.

Timestamp: [24:40-26:07]

When Retention Curves Don't Just Flatten - They Go Up

There's something even better than flat cohort retention curves. The absolute best-case scenario is when your curves don't just stabilize - they actually improve over time.

The Ultimate Achievement:

"The best of the best is cohort curves that don't just get flat but they actually go up over time." - David Lieb

What Upward Curves Mean:

• Increasing Usage: Users who stick with you start using the product MORE over time
• Deepening Value: The product becomes more valuable the longer someone uses it
• Habit Formation: Usage patterns strengthen rather than weaken
• Product-Market Fit Plus: You've achieved something beyond basic retention

How to Achieve Upward Curves:

Combine Multiple Techniques:

• Better Product: Continuous improvement that adds value
• Better Targeting: Users who are perfect fits for your product
• Network Effects: Product gets better as more people use it
• Improved Onboarding: Users reach deeper engagement faster

The Compounding Effect:

When you execute well across multiple improvement methods:

1. Flat Curves First: Achieve basic retention stability
2. Increasing Curves: See usage grow within cohorts over time
3. Better Cohorts: Each new cohort performs better than the last
4. Confidence Signal: You should be feeling really good about your business

The Strategic Validation:

Upward-trending cohort curves are one of the strongest possible signals that you've built something truly valuable that becomes more essential to users over time.

What This Enables:

• Predictable Growth: You can model future user base expansion
• Strong Unit Economics: Users become more valuable over time
• Defensive Moats: Deeply engaged users are harder for competitors to steal
• Investment Attractiveness: VCs love businesses with improving cohort curves

Timestamp: [26:07-26:43]

From Retention Analysis to Multi-Billion Dollar Visualization

The ultimate goal of cohort retention analysis isn't just measurement - it's building a sustainable, growing business. The layer cake chart shows you exactly what billion-dollar user growth looks like.

From Triangle to Layer Cake:

The Transformation Process:

1. Start with Triangle Chart: Count users from each cohort using your product each month
2. Align to Absolute Time: Slide rows to show real calendar months instead of relative months
3. Stack the Layers: Each month shows total active users, but broken down by original cohort

What the Layer Cake Reveals:

• Total User Growth: The top line shows your overall active user trajectory
• Retention Composition: Each layer shows which original cohorts contribute to current activity
• Cumulative Value: Growth isn't just new users - it's retained users from ALL previous cohorts

The Beautiful Chart You Want to See:

"If you see a layer cake that looks like this - the top line is growing really nicely and it's composed of thick layers coming from old cohorts - this is like the most beautiful chart that you'll ever see in your startup." - David Lieb

Example Analysis (December Data):

• Total Active Users: Almost 600 users in December
• Not Just New Users: Composed of users from ALL previous months who stuck around
• Compounding Growth: Each month adds new users WHILE retaining old ones
• Sustainable Foundation: Thick layers from old cohorts prove lasting value

The Multi-Billion Dollar Connection:

What This Chart Represents:

"This layer cake graph is hopefully the start of what could be a multi-billion dollar company." - David Lieb

Why Layer Cake = Big Business:

1. Compounding Growth: New users add to existing base rather than replacing churned users
2. Predictable Expansion: You can model future growth based on cohort patterns
3. Strong Unit Economics: Users stick around and continue providing value
4. Investor Confidence: This chart pattern is what VCs look for in potential unicorns

Success Recognition:

"If you see this, congratulations - you're off to the races." - David Lieb

Timestamp: [27:02-28:30]

The Final Word on Turning Analysis Into Action

Cohort retention analysis is powerful, but it's not a crystal ball. Here's how to use these insights to actually improve your business and build something people truly want.

The Complementary Approach:

Quantitative + Qualitative:

"You obviously want to go talk to your users in person, hear what they're saying - this is the qualitative feedback that's going to actually give you insights about your product." - David Lieb

What Cohort Analysis Can and Can't Do:

• What It Tells You: Whether you're on the right track and things are working
• What It Doesn't Tell You: What specifically to change about your product
• The Gap: You need user conversations to understand the "why" behind the numbers

The Clear Signal for Action:

"If you look at your cohort retention curves and they don't get flat, the one thing you can be sure of is that you need to get out there, talk to your customers, understand what's going on and hopefully make something that they want." - David Lieb

The Action Framework:

1. Measure: Build proper cohort retention curves
2. Diagnose: Look for flatness (or lack thereof)
3. Investigate: Talk to users to understand why curves behave as they do
4. Iterate: Apply the five improvement methods based on user feedback
5. Measure Again: See if changes move curves toward flatness

The Ultimate Goal:

The entire point of this analysis is to answer Y Combinator's foundational question: "Did we make something people want?"

The Definitive Answer:

• Flat curves: You're on your way to making something people want
• Non-flat curves: You need to get back to customer discovery and product iteration
• Upward curves: You've definitely made something people want and are building a potentially massive business

The Blessing:

"I wish for each of you a flat cohort retention curve in your future." - David Lieb

Timestamp: [28:30-29:14]

Essential Insights:

1. There are five strategic levers to improve cohort retention: product improvements, better user targeting, cohort analysis, onboarding optimization, and network effects - Often acquiring better users or improving onboarding is easier than major product changes
2. The holy grail isn't just flat curves but curves that go up over time - This indicates users become more engaged the longer they use your product, creating a defensive moat and predictable growth
3. The layer cake chart transforms retention data into a visualization of billion-dollar potential - When thick layers from old cohorts stack up with growing top-line usage, you're seeing sustainable, compounding growth

Actionable Insights:

• When curves aren't flat, immediately slice cohorts by different dimensions (country, device, acquisition channel) to identify which user segments actually retain well
• Invest heavily in first-user experience and onboarding - it's often the cheapest and easiest way to improve cohort performance
• Use cohort analysis as a diagnostic tool to know whether you're on the right track, then talk to users to understand what specifically needs to change
• Aim for the layer cake pattern where each month's active users include thick contributions from all previous cohorts, not just recent acquisitions

Timestamp: [21:28-29:14]

Companies & Products:

• Google Photos - Case study showing how targeting the wrong demographic (Gen Z) led to poor retention despite successful user acquisition
• Google - Example of company-wide strategic decisions about targeting younger demographics that impacted product retention metrics

Concepts & Frameworks:

• Five Cohort Improvement Methods - Product enhancement, better user targeting, cohort analysis, onboarding optimization, and network effects
• Layer Cake Chart - Visualization technique showing how total active users are composed of retained users from all previous cohorts
• Network Effect Density - The principle that products become more valuable as networks become denser rather than just larger
• First User Experience Optimization - Strategic focus on activation and onboarding as the most cost-effective retention improvement
• Upward Cohort Curves - The holy grail metric where retention not only flattens but actually improves over time within cohorts
• Quantitative + Qualitative Analysis - The framework combining cohort retention measurement with customer conversations for actionable insights

Timestamp: [21:28-29:14]