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Trying to make a dent in the universe with the inbound marketing start-up HubSpot. Previously studied entrepreneurship and computer science at MIT Sloan and Amherst College.

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Why Shopify's churn article doesn't matter for 95% of SaaS companies

  
  
  

Shopify recently posted an article on defining churn rate and the 'correct' way to calculate the metric and the limitation of the more standard approach.  Steven Noble is completely right in the importance of churn.  It's a massively important metric for SaaS companies and can kill even the most successful companies and cap potential any revenue potential if not held in check.  However his assertion that many companies get it wrong is incorrect (well at least for the reasons he states)

Why the Shopify article on churn is wrong for 95% of SaaS Companies

Where the article fails is in the proposition that most companies are calculating churn wrong because of the impact of churns from new customers within the period.  

"The problem here is that the [number of churns over period] value is affected by the entire period but the [number of customers at beginning of period] value is a snapshot from the beginning of the period. This might not have much impact if new customers only make up a small percentage of your user base but for a company that's growing this can lead to some major misinterpretations."

Noble goes on to describe how you have to not only account for the customers at the beginning of the period but also the customers who churn over the period.  He shows some interesting math on the topic - but what he misses is that for most SaaS companies they bill customers monthly (at the shortest interval) so customers only have one opportunity to churn in a month - and similarly new customers can't churn within the first month they sign up. For instance if you have a product that is $100 a month, and a customer signs up and pays you on the 15th of July - that customer can't churn until their next billing date, the 15ht of August.  So that 'churn from new customers' isn't relevant within the month your calculating churn. 

The real open questions on defining churn

There are however some more interesting questions surrounding the right way to calculate churn.  Specifically there are two large questions we think about at HubSpot:

  • Should upsell be included in churn?
  • Should customers locked into long term contracts be included in churn?

For HubSpot we've determined that we should actually calculate both customer churn (excluding upsell) and revenue churn (which includes upsell and is weighted by the recurring revenue from each customer).   Customer churn ensures that you're delivering continued value to all your customers and MRR churn ensures you're getting the economics of the business correct.

For locked-in customer we've determined that yes - you should include those customers.  The simple reason for this is that if only looked at customers up for contract renewal you could incorrectly move the metric short term by selling more month-to-month deals (at a higher overall churn rate) once at steady state.  For instance if customers who sign 12-month upfront contracts churn naturally at 1% monthly - when the contract was up this month the end of the year they'd have a 1-(.99%)^12 = 12% retention rate in that one month their contracts are up.  If you instead sold month-to-month last month that churned at a higher 2% monthly rate, those month-to-month contracts would also renew this month and blend in with the 12% churn from annual contracts lowering the calculated churn rate that month even though overall they were a worse cohort of customers.

As illustrated by this topic SaaS metrics are at best inconsistently applied and can be really hard to compare from company to company.  The best thing to do is find an approach you can apply consistently internally and work to push those metrics in the right direction - and worry less about the exact benchmarks you're hearing from friends and VCs. 

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Comments

Interesting points but I have a few quibbles. 
 
So while in my post I talk about sign ups I also simplified everything to an unsegmented perspective. While I noted this simplification at the end I should have stressed the point a little more clearly.  
 
When I talk about new customers entering into your count they are only allowed to enter your count when they are capable of churning. Whether for your product that means at sign up, having paid your first bill, or something else, that moment has to happen somewhere (do we say somewhen?). And those entries into your count aren't necessarily going to happen evenly. 
 
So yes, while someone can't churn the moment they sign up there is a moment they can churn. And it's that uneven growth that concerns me. 
 
Now if you use churning as not paying a bill this makes for a funny denominator because customers keep jumping in and out. 
 
But this brings me to my other quibble. We don't think a customer can only churn on their bill due date. We think that using the signal of a customer telling us they are churning by cancelling is important to measure. Part of the reason I mentioned in the post: being current. If we are doing something that is making our customers unhappy we want to know as soon as possible. That means the moment a customer cancels our churn rate goes up and we can respond. 
 
The other reason is a bit more subtle: statistical significance. If some group of customers are motivated to churn by a certain event then their cancellation events are probably close together by time. That will create a significant blip in our churn rate in this period (e.g. in a weekly churn rate). If we instead count the churns on their would be billing dates then we've just diffused the signal to the point where you might not detect it anymore. 
 
This of course raises the question of how to count customers who let their payment lapse who didn't cancel. We actually find there is good reason not to count these customers as churned as a high percentage of them self cure. Eventually they do need to be counted as a churn, and when to do that is a hard question. We are currently exploring some actuarial techniques to determine what is the right answer for us. 
 
I think in the end what to count as a churn is going to have to be decided for each company and each customer base. As you note whether you bill monthly, or annually, or a mixture, is going to inform this decision. 
 
But as I said in the post, determining what is a "cancellation" wasn't answered in that post. Instead I gave a way you can get a churn rate with desirable properties given cancellations that can occur irregularly. 
 
If you want to count churns at unpaid bills the you will probably be using something like the "The predictive modelers' fancy." 
 
I appreciate your feedback and your thoughts. And I completely agree with you that if you are tailoring your metrics just so they can be told to VCs and friends you're doing it wrong.
Posted @ Monday, November 28, 2011 11:19 PM by Steven H. Noble
If I could ask you to note one correction though. In my comment here I have talked about definitions for churn but in the blog post I go out of my way not to. What I define there is "churn rate."
Posted @ Monday, November 28, 2011 11:22 PM by Steven H. Noble
Steven - Thanks for you thoughtful response. Focusing on the the moment someone cancels (vs churns) makes a lot of sense and can be insightful for most businesses. Thanks.
Posted @ Wednesday, December 07, 2011 8:01 AM by Brad Coffey
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