Toward Fair and Sustainable Regional Development: A Multidimensional Framework for Allocating Public Investments in Türkiye

Regional disparities pose persistent challenges for balanced and sustainable development in Türkiye, where provinces exhibit prominently heterogeneous socioeconomic structures, capacities, and investment needs. This study proposes an integrated, data-driven framework for allocating public investments across provinces by jointly addressing development efficiency and spatial equity. A dataset of 109 indicators for 81 provinces was compiled and standardized, and Principal Component Analysis, followed by multiple clustering algorithms (K-Means, Gaussian Mixture Model, Fuzzy C-Means), was used to derive robust provincial development profiles. National policy priorities were quantified through a document-based assessment of the 12th Development Plan (2024–2028), enabling the construction of nine strategic investment categories aligned with national objectives. These components were incorporated into a multi-objective optimization model formulated using the ε-constraint method, where total utility is maximized subject to an adjustable equity constraint based on a Gini-like parameter. Results reveal a clear efficiency–equity trade-off: low inequality tolerance yields uniform but low-return allocations, whereas relaxed equity constraints amplify concentration in high-capacity metropolitan provinces. Intermediate equity levels (G = 0.3–0.5) generate the most balanced outcomes, supporting both development potential and spatial cohesion. The proposed framework offers a transparent, reproducible decision support tool for more equitable and strategy-aligned public investment planning in Türkiye.