وحید محمودی

This study investigates the impact of global crude oil price fluctuations on the volatility of the Iranian Rial–U.S. Dollar exchange rate over the period November 2011 to August 2025. Using daily data and employing GARCH-family models—including GARCH(1,1), EGARCH(1,1), and GJR-GARCH(1,1,1) under heavy-tailed distributions—we examine whether oil price shocks influence the mean and conditional variance of exchange rate returns. The results indicate that higher oil prices significantly appreciate the Rial, reflecting Iran’s dependence on oil revenues and foreign exchange inflows. Volatility dynamics reveal strong persistence, with shocks exhibiting long memory. Asymmetric effects are also evident: negative oil price shocks increase exchange rate volatility more than positive shocks, highlighting the destabilizing role of downturns in global oil markets. Diagnostic tests confirm the adequacy of the estimated models, with EGARCH and GJR specifications providing the best fit. The findings underscore three key policy implications. First, Iran’s exchange rate remains highly sensitive to oil revenues, reinforcing the need for structural diversification. Second, the persistence of volatility complicates short-term stabilization, demanding long-term reserve and fiscal policies. Third, the asymmetric impact of oil downturns calls for proactive risk management to mitigate volatility in times of declining oil prices. Overall, the study provides new evidence on the oil–exchange rate nexus in an oil-exporting economy, offering lessons for macroeconomic management under external shocks. Robustness checks — including Bai–Perron breakpoint tests and alternative model specifications with event dummies — confirm the main findings.