Linkages between External Reserves and Economic Performance in Nigeria, 1981-2018: Bounds Test and ARDL Approaches

Aims: This study seeks to explore a two-way relationship between Nigeria’s economic performance, measured by the GDP, and her stock of foreign reserves over time.

Study Design: It uses secondary data - documented time series of Nigeria’s gross domestic product (GDP) and foreign exchange reserves (FER) – collected from various volumes of the Central Bank of Nigeria (CBN) Statistical Bulletin. The annual time series data cover a period of 38 years, from 1981-2018.

Methodology: The time series properties of the variables were verified using the Augmented Dickey-Fuller (ADF) unit roots’ test procedure. Also, the Bounds test technique was used to test for cointegration while the autoregressive distributed-lag (ARDL) and error correction models were estimated to analyze short- and long-run relationships between the variables. Relevant diagnostic tests were carried out to validate the resultant model estimates.

Results: Results of unit roots’ test reveal both GDP and foreign reserves as I(1) series. Bounds test for the GDP model revealed an observed F-statistic (.421) that is less than the critical lower bound F-statistic (4.94) at P=.05 and cointegrating relationship was not confirmed. However, Bounds test for the foreign reserves revealed an observed F-statistic (6.445) lager than the critical upper bound F-statistic (5.73) at P=.05 and cointegration was established leading to specification of a long-run error correction model (ECM). Result of ARDL model estimation shows that only one-year-lag of GDP was significant (P=.05) and positive in explaining variations in the current GDP. Previous year’s values of both GDP and foreign reserves have positive influence on the long-run foreign exchange with over 81.8% explanatory power. The adjustment coefficient of the error correction equation is highly significant (P=.001) with the desired negative sign, implying that previous periods’ errors are correctable by adjustments in the subsequent periods, and convergence is attainable. Granger-Causality test result revealed a unidirectional causality that runs from GDP to the external reserves.

Conclusion: The study establishes a long-run relationship between stock of foreign reserves and economic performance in Nigeria. The finding corroborates the view that a booming economy has the propensity to attract foreign direct investment thereby boosting the stock of the country’s foreign reserves. To attract more FDI in the critical sectors of the Nigerian economy, the government should create enabling and investment-friendly environment, implement policies and programmes capable of amplify ease-of-doing-business, and boost investors’ confidence in the economy.