The user list generation server identifies a candidate set of users in the same group as at least one user in the original set of users in 404. As described above, the user list generation server can identify users who are assigned a same group identifier as one or more of the users in the original set of users. For example, if a user in the original set of users is assigned a group identifier that corresponds to gardening and another user is also assigned a group identifier that corresponds to gardening, that other user can be identified in the candidate set of users. Thus, if a user is in a same user interest group as at least one user in the original set of users, then the user can be identified as a candidate user to be added to the user list.

Next, the user list generation server generates an intermediate list with the candidate set of users (406). Users that are part of the candidate set of users can be added to the intermediate list. The intermediate list may also include one or more of the users from the original user list, as described in reference to FIG. 1. The intermediate list can be a user action group that has been expanded based on membership of users in the same user interest group(s). The intermediate list can then be used in post-processing, ranking, and/or selection techniques in order to determine which users can receive relevant digital components. Thus, post-processing techniques can be used to refine the intermediate list (e.g., the expanded user action group) such that users that may not be as similar or that may not be likely to perform some specified action(s) associated with the intermediate list can be filtered out from the intermediate list. Those users that are filtered out may not receive digital components that relate to the specified action(s) associated with the intermediate list.