analysis of the income distribution structure in iran's development plans

This study analyzes income distribution in iran across six national development plans (1989–2022), focusing not only on inequality measures—such as the q_5/q_1 1 ratio, palma ratio, hoover index, and lorenz curves—but also on the underlying structure of income inequality. a key contribution of this research is the combined assessment of both the level and the structure of inequality over time. logarithmic differentiation is applied to determine whether changes stem from the top or bottom of the income distribution. additionally, inspired by sitthiyot and holasut (2020), a composite index is developed by combining the gini coefficient with decile-based ratios, allowing for structural differentiation even when gini values are constant. the findings indicate that despite some fluctuations in standard indices, the overall structure of income distribution remained largely stable. modest improvements occurred during the third and sixth development plans, while the first, second, and fifth plans showed little to no progress. over the study period, the gini coefficient declined by 8.5%, the hoover index by 9.8%, the palma ratio by 18.2%, and the q_5/q_1 ratio by 20.7%. these results suggest limited structural change and highlight the need for more targeted and effective redistributive policies—especially under macroeconomic pressures such as inflation and external shocks.