This four part series of research briefs summarized detailed analysis of attendance and chronic absenteeism in Oregon. Brief 1 highlighted the importance of tracking chronic absenteeism rather than average daily attendance. The second brief in this series focused on student outcomes and attendance. Research suggests, and Oregon Department of Education data confirm, that chronically absent students have poorer academic outcomes and graduate at lower rates that their peers. The third brief highlighted the ability of schools to use daily attendance data to find trends and patterns that are relevant to students in their building. This fourth and final brief in the series provides an overview of some of the challenges presented by focusing too much on excused and unexcused absences. Data from the sample schools suggest that certain student groups, like economically disadvantaged students, students with a race or ethnicity other than White, students and English Language Learners, may be more likely to have unexcused absences than their peers. [For "A Statewide Look at Attendance and Chronic Absenteeism in Elementary Schools in Oregon. Chronic Absenteeism in Oregon Elementary Schools. Part 1 of 4. September 2016. Research Brief Series," see ED578927; For "Connecting Attendance and Academic Outcomes. Chronic Absenteeism in Oregon Elementary Schools. Part 2 of 4. September 2016. Research Brief Series," see ED578928; For "Daily Attendance Data. Chronic Absenteeism in Oregon Elementary Schools. Part 3 of 4. September 2016. Research Brief Series," see ED578929.]