Review of Data Visualization Applications in Activity Reports of Istanbul District Municipalities

Our age has resolved critical actions in managerial processes such as storage and retention of data, creating a huge pile of data whose processing and visualization has become valuable for making sense of and expressing it. Visualization provides a powerful representation to extract meaning and discover insights from data, strengthening the narrative that institutions and organizations use in their reports. However, this is not as straightforward as it may seem: visualization is difficult to use and complex to implement, and when applied incorrectly, it creates greater complexity and makes the story it tells multi-layered. Visualization therefore needs to be faithful to its context and appropriate for its target audience, taking the data-to-ink ratio into account.
Within the scope of this study, the data visualization techniques used in the most recent (2024) annual activity reports of the district municipalities of Istanbul, published as open access, were identified and classified through a mixed-methods design combining document analysis and content analysis. A total of 9,742 pages across the reports of 39 municipalities were reviewed (Şile Municipality was excluded, as its 2024 report was unavailable), and the chart types and features used were coded by dual coders with over 90% agreement. The findings indicate that municipalities predominantly rely on basic-level visualizations, particularly first-level chart types such as bar, line, and pie charts, and that tables are largely transferred into reports without formatting or customization. A low data-to-ink ratio, frequent use of three-dimensional and decorative chart elements, and limited use of spatial mapping and interactive presentation techniques were also observed. Errors in the preferred visualization formats and chart types were identified when evaluated against universal design principles. This study is important for examining and evaluating visualization techniques in the annual reports of public institutions, offering a baseline for improving the accessibility and communicative effectiveness of municipal reporting practices.

Data visualization, Data-based decision making, reporting, Visual communication in public services, Data analytics in public services

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