An Autoregressive Distributed-Lag Modeling Approach to Nigeria’s External Reserves Dynamics

Abstract

The objective of this study was to develop and analyze a regression model that explains the dynamics of foreign exchange reserves in Nigeria by examining the short-run and long-run impacts of some macroeconomic variables (exchange rate, inflation, interest rate, crude oil price, and real gross domestic product) on foreign reserves in Nigeria from 1986 to 2018. The data were sourced from the publications of the Central Bank of Nigeria (CBN) and World Bank. Unit root and co-integration tests were performed on the variables before estimation. An empirical multivariate autoregressive distributed-lag model (ARDL) was identified, specified, and estimated with the aid of EViews econometric software. Diagnostic tests for serial correlation (Breusch-Godfrey serial correlation LM test), normality (Jarque-Bera test), stability (CUSUM-of-squares test), and forecasting performance test were conducted to evaluate the estimated model. The study found that the estimated ARDL model could provide information on the behaviour of foreign exchange reserves in Nigeria. The regression results showed that none of the explanatory variables (exchange rate, inflation rate, interest rate, crude oil price, and real gross domestic product) shared contemporaneous and lagged relationship with foreign reserves dynamics in Nigeria. However, in the long run, only the previous value of foreign reserves was significant in explaining foreign reserves dynamics in Nigeria during the sample period. Given that foreign reserves play an important role in the design and evaluation of current and future macroeconomic policies aimed at achieving trade balance, the study makes the following recommendations: (1) government policies directed at managing and improving foreign reserves should largely consider the short-run and long-run behaviour of foreign reserves and these policies should be pursued with high degree of transparency because foreign reserves dynamics largely find explanation in adaptive expectation in Nigeria, (2) policy makers should ensure the evolution of appropriate exchange rate policies and regimes that will enable the economy build its reserves and adequate and balanced reserves should be accumulated to help to smoothen out the volatility in the exchange rate only in the short run, (3) government and the relevant agencies should block all foreign reserves leakages in the economy by ensuring that foreign exchange allocation and utilization are purely for genuine economic purposes and build fiscal buffers through the replenishment of the Excess Crude Account or the Sovereign Wealth Fund, and (4) the implementation of appropriate policies to facilitate the diversification of the Nigerian economy along areas of key comparative advantage (such as agriculture and small scale labour-intensive manufacturing).