Section 4.1.3 of the SFD manual gives examples of the type of information to collect that will help identify the extent to which sanitation technologies and services are meeting the needs of the urban poor. The type of information includes, for example, the sanitation technologies the urban poor rely on, levels of access and affordability of different service options. This information will provide you with evidence to write about inequalities in access to sanitation services in the SFD Report.
If you want to develop this further and prepare an SFD Graphic to highlight inequalities (for example to show how the SFD Graphic for an area with high levels of unimproved services compares to the city as a whole), this is explained further in FAQ #35: Can I use the SFD process to make an SFD for a sub-area within a city, or for a particular sub-group within the city population?