Why doesn’t New Customers + Repeat Customers = Customers?

Why doesn’t New Customers and Repeat Customers add up to Customers?

Executive Summary

We count new and repeat customers irrespective of each other. If a customer placed their acquisition order within the date aggregation (day/week/month etc.), they are counted as a new customer. If a customer places a repeat order within the date, they are counted as a repeat customer. If a customer places both their acquisition order and a repeat order within the date aggregation, they will be counted as 1 new customer and 1 repeat customer.

This double counting can result in New Customers + Repeat Customers being higher than the Customers figure when customers place their acquisition and repeat order within the date aggregation.

Example: In May we acquire 100 new customers, and 100 repeat customers -- who acquired in April or earlier -- come back to make another purchase. Assuming none of the customers who were acquired in May place a second order within that month, we'll have the following counts for the month -- customers: 200, New Customers: 100, Repeat Customers: 100 for May. However, let's say 25 of those customers who were acquired in May place a second order before the end of the month. Those customers will now be counted towards Repeat Customers as well as New Customers, resulting in the following counts for the month -- Customers: 200, New Customers: 100, Repeat Customers: 125. Additional Note: First-time orders which include only gift cards are not counted as new customers by Shopify, but will be counted as new customers by Source Medium.

Module
Uniqueness
Examples
Executive Summary
Daily
If customer buys 3 times in 1 day, customer gets counted once as a New Customer and once as a Repeat Customer for the day. If customer buys 3 times over 3 days, customer gets counted once as New Customer on the first day and once as a Repeat Customer on each subsequent repeat purchase date. If customer buys 3 times over 3 days, and the date gets rolled up to a week view, customer gets counted once as New Customer and twice as a Repeat Customer. A customer can only be counted once as a New Customer, ever.
Repurchase Analysis
Monthly
If customer buys once in July and twice in August, customer is counted once as a New Customer in July and once as a Repeat Customer in August. If customer buys 3 orders in July, customer is counted once as a New Customer and once as a Repeat Customer.
Last Order Analysis
Absolute
If customer buys once in July and twice in August, customer is counted once in August on date of third purchase and categorized as Repeat Purchaser. If customer buys 3 times in July, customer is counted once on date of third purchase and categorized as Repeat Purchaser.
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