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Understanding Cohort Analysis

The cohort tables within your Retention tab measure your customer retention over time.

Written by PolarBears

Overview

Cohort analysis helps you understand how groups of new customers behave over time—specifically, how often they return and how much revenue they generate. This article walks you through how to:

  • Understand what a cohort is

  • Read and interpret the Cohort Tables

  • Analyze customer behavior in the Cohort Evolution Graph

  • Understand how Polar calculates cohort data, and how it differs from Shopify

What is a Cohort?

A cohort is a group of customers who share a common trait—typically, the month they made their first purchase. Cohort analysis helps you track and compare the behavior of these groups over time.

This allows you to answer key questions such as:

  • What percentage of customers return 6 months after their first purchase?

  • Is my customer retention improving over time?

  • How do promotions or product changes affect long-term customer loyalty?

You’ll find cohort tables and graphs in the Retention tab. These tools help you analyze repeat purchase behavior and identify trends across different customer groups.

🎥 Watch the video below for a walkthrough of the Retention tab and cohort tables.


How to Read the Cohort Tables

The Retention cohort table uses a clean, single-metric layout. Each table shows one metric at a time, and every cohort has its own Cohort size and First order columns, followed by Month 0 through Month N—so acquisition and each following period read at a glance.

Choosing a metric

Select the metric you want from the metric selector and the table redraws for it. The table defaults to Retention Rate, and you can switch between:

  • Retention Rate – the percentage of the cohort that has returned to purchase, accumulated through each period (the default view)

  • Customers – the number of customers from the cohort who purchased in that specific period

  • Orders – orders placed by the cohort in each period

  • Total Sales

  • Net Sales

  • Gross Margin

  • LTV – cumulative lifetime value per customer, accumulating as periods progress

  • LTV:CAC – lifetime value relative to customer acquisition cost

Because each metric represents a fixed view, there are no separate cumulative/non-cumulative or absolute/relative toggles. For example, select Retention Rate for a cumulative, relative view of retention, or Customers for period-by-period counts.

Period basis

Use the period basis control to choose how columns are defined:

  • Calendar periods (default) – Month 0 is the customer's acquisition month, and each following column is the next calendar period.

  • Rolling windows – periods are measured from each customer's own first order, giving a lifecycle-based view rather than a calendar-aligned one.

CAC indicator

When a CAC-based metric such as LTV:CAC is selected, a live indicator tells you whether the CAC being used is blended (across all channels) or scoped to the channel or campaign you've filtered by—so you always know which acquisition cost the ratio reflects.

📊 Horizontally (Row by Row)

This shows how a single cohort behaves over time.

For example:

  • In April 2024, you acquired 1.4k new customers.

  • By July 2024 (3 months later), 1.90% of them made another purchase.

When viewing a period-by-period metric such as Customers, each column reflects only purchases made in that specific period. If a customer buys twice (e.g. in November and again in January), they're counted in both periods separately.

📈 Vertically (Column by Column)

This shows how all cohorts behave at a specific time after their first purchase.

For example:

  • You might notice that Month 1 and Month 2 after purchase show the highest repurchase rates.

  • This insight can inform your post-purchase email flows and CRM strategies.

🔀 Diagonally (Same Purchase Month Across Cohorts)

Looking diagonally shows trends during specific periods like holidays or promotional campaigns.


For example:

  • If March shows unusually high repurchases across several cohorts, a successful campaign likely drove that behavior.

⚠️ Note: The cohort analysis only considers sales from new customers, not all sales made in a period.


Filtering and Customizing Your Cohort View

You can take your cohort analysis further by applying filters and customizing how data is displayed.

Filter Options:

You can break down your cohorts by:

  • Product collection – Based on the first item a customer purchased

  • Acquisition source – Using UTM tags or data pulled from Klaviyo

  • Shopify filters – Such as customer tags, or geographic location

These filters help answer questions like:

  • Which product categories drive the highest repeat purchase rates?

  • Do customers acquired via Meta ads return more frequently than those from email?

  • How does retention vary across different customer segments?


How to Read the Cohort Evolution Graph

The Cohort Evolution Graph shows how the cumulative lifetime value (LTV) grows over time for a specific customer cohort.

  • Month 0: The customer’s first 30 days from their initial purchase.

  • As you move along the timeline, you’ll see how much more revenue that cohort has generated.

  • Hover over each point to view exact values and the total number of customers in that cohort.

  • Add breakdowns & top segments to identify how customers interact with your store after a purchase & what revenue they drive over time.

Polar will automatically pre-select the top 3 performing segments to help populate the chart meaningfully. These top segments are typically:

  • The top 3 SKUs or product types (depending on your breakdown)

  • Determined by total sales volume from first orders

The customer count stays the same across time—only the LTV value increases as more purchases occur.


Cohort Calculations

How cohort periods are defined depends on the period basis you choose:

Calendar Months

Rolling Window

Month 0

Starts on the 1st of the month

Starts on the exact purchase date

Month progression

Calendar months

Every 30-day period from first purchase

  • With calendar periods (the default), Month 0 is the acquisition month and each column is a following calendar month—matching Shopify's calendar-month cohorts.

  • With rolling windows, periods are measured from each customer's exact first-order date, which can produce percentages that differ slightly from Shopify's.

Example (rolling windows)

  • A customer purchases on November 15th.

    • Month 0: Nov 15 – Dec 14

    • Month 1: Dec 15 – Jan 14

    • Month 2: Jan 15 – Feb 14

  • In Shopify (calendar months):

    • Month 0: November

    • Month 1: December

    • Month 2: January

The rolling-window method reflects customer behavior based on actual timing from first purchase rather than calendar boundaries.

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