I've always assumed that Populations (formerly Root Relationships) were necessary to use Journey Builder.

However, I was recently informed by Marketing Cloud Support that they are not required. Another Salesforce employee told me that you only need them if you are using the Contact Attributes in your Journey.

So, which of these statements are true?

3 Answers 3


There's a lot of confusion on this topic, which isn't helped by the amount of mis-information currently in circulation.

Populations are of particular relevance when the Contact record is initally created. That is, when a Subscriber is injected into a Journey for the first time. Contact Records need to have an email address, and this is derived from the Population (much like when you use a Sendable Data Extension and the email address is derived from the email field).

While the Contact's email address can be overridden within a Journey by setting the Channel Address Order or the Entry Source, it this won't change the Contact's email address in All Contacts.

So, what happens if you create a Journey without a Population? Well, I've put this to the test and played a couple of scenarios, creating cardinal relationships in Contact Builder (without a Population) and a simple Journey with a Decision Split and Update Contact Data Activites:

Attribute Group Journey

Contact Records do not Exist in Marketing Cloud

If the Contact Records do not already exist, then they will attempt to enter the Journey, but fail at the Event stage with the error:

Failed - ExactTarget.JourneyBuilder.Events.Event.FilterResult: Error binding data bound member.

Contact Record already exists in Marketing Cloud

If the Contact Record already exists in Marketing Cloud, then a Population isn't required. I tested by creating the Contacts using the Contacts API method and when I fired the Event, Contacts were injected into the Journey and correctly passed through the Decision Split Criteria and updated the Data Extensions that were configured:

Journey Result


So it appears that it is actually possible to use Journeys without a Population, providing that the Contacts exist there in the first place. One scenario that I can think of is that if a Contact is originally created in a Parent Business Unit (for example, via a Population in Contact Builder), then a Population won't be required in any of the child Business Units if you are sending to the same Contact, as unlike Attribute Groups and Populations, Contacts are global across all Business Units.

However, before you run out and setup Populations with every single possible customer record, bear in mind that you are billed for Contacts, which includes the number of records in your Population, even if they don't yet exist as a Contact Record. :-/

  • 1
    Marketing Cloud Documentation seems to lack explanations or detailed information regarding Populations, I can not seem to grasp the idea of it and the purpose it serves, your answer has helped me understand it a bit more but it is still up in the air with why someone would choose to use this feature considering its optional and more costly for clients. Aug 10, 2017 at 12:28
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    My two cents... A design pattern I'm increasingly using is importing all my Contacts to All Subscribers and doing away with populations entirely. They're problematic as unlike the previous Root Data Extension concept, you can't relate new DEs you add to your Contact Model to your Population data extension in any other way than defining a relationship to the ContactKey. The other challenge I have with populations is you run the risk of being double billed for the same contact if they appear in two populations in the same or different Business Units.
    – Macca
    Aug 11, 2017 at 0:24
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    @Macca if the same contact exist in different population with same contact key you will not be billed for duplicate contacts.Marketing cloud bills only for the unique contacts. May 18, 2018 at 6:36

This is the latest: Populations are NOT required in Journey Builder. They used to be, they no longer are as the PM team modified JB to allow for use of just sending to DEs. While you still may use populations, you do not have to and can specify channel, and fields (email, mobile) which you wish to send to in JB settings. Thanks.


While this was/is the case for 'Entry Events', Salesforce is pushing 'Journey Builder Audiences' on customers pretty hard now. With audiences the documentation notes that:

Note: If no contact record exists in the Marketing Cloud for a person entering this journey, Journey Builder creates one.

I would interpret that to mean that a new record is added into the All Contacts list automatically, and one less reason to use Populations.

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