Forecasting Nigeria's Real Gross Domestic Product Using the ARIMA Model: Out-of-Sample Evaluation and Projections to 2030

Abstract

This study examines the predictive performance of the Autoregressive Integrated Moving Average (ARIMA) model in forecasting Nigeria's real Gross Domestic Product (GDP) from 2025 to 2030. Annual real GDP data (1981–2019) from the Central Bank of Nigeria were analyzed using the Box–Jenkins methodology. This paper fills a major scholarly gap by executing out-of-sample validation using observed post-estimation provisional holdout data (2020–2024) to verify baseline parameters before projecting and establishing a transparent parsimonious macroeconomic benchmark. The series was non-stationary at level but became stationary after first differencing, which led to selecting ARIMA (1,1,1) based on minimized information criteria. Real GDP is projected to increase from ₦82,334.34 billion in 2025 to ₦93,506.79 billion in 2030, offering a reliable framework to support evidence-based budgeting, macroeconomic planning, and policy formulation.