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Monetary Policy, Exchange Rate Shocks, and Asset Prices in a Small Open Frontier Economy: An Integrated Multi-Horizon Distributional Analysis

This study utilizes an integrated multi-horizon distributional analysis of Ghana's equity market from 2014 to 2024 to reveal that domestic monetary policy shocks have a weak and inconsistent impact on stock returns, whereas global oil prices and short-term funding costs play a more significant, state-dependent role in driving market dynamics.

Original authors: Isaac Nyame, Gabriel Osei Forkuo

Published 2026-07-21

📖 4 min read☕ Coffee break read

CC BY 4.0

Original authors: Isaac Nyame, Gabriel Osei Forkuo

Original paper licensed under CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). ✨ This is an AI-generated explanation of the paper below. It is not written or endorsed by the authors. For technical accuracy, refer to the original paper. Read full disclaimer

Imagine the economy as a giant, bustling kitchen where the central bank is the head chef. In fancy, well-stocked kitchens (like those in advanced countries), if the chef turns up the heat (raises interest rates), the whole kitchen slows down: the ovens cool, the ingredients get expensive, and the food prices drop. This is the "monetary policy transmission" channel, a well-known rule in economics. But what happens in a tiny, frontier kitchen with only a few pots, a shaky stove, and ingredients that arrive on unpredictable boats? Does turning up the heat actually change the meal, or does the kitchen just sputter and ignore the chef? This question sits at the intersection of finance and economics, exploring how government decisions about money ripple through to the value of companies (stocks). It matters because if the chef's knob doesn't actually control the stove, then the recipes for managing the economy might need a total rewrite.

Now, let's peek into the kitchen of Ghana, a "frontier" economy where the stock market is small and thinly traded. A team of researchers decided to investigate whether the Bank of Ghana's main tool—the policy interest rate—actually controls the prices of stocks on the Ghana Stock Exchange. They looked at data from January 2014 to December 2024, a period filled with wild swings in inflation and currency values. Instead of just asking, "Does the rate go up, do stocks go down?" they used a super-sophisticated magnifying glass to look at the market in three different ways: checking if the relationship changes when the market is happy versus when it's terrified, seeing how the connection changes over different time horizons, and testing if other factors might be the real chefs in the kitchen.

The results are a bit of a plot twist. The researchers found that the domestic policy rate is surprisingly weak in its ability to move the stock market. It's as if the head chef turns the knob, but the stove barely flickers. When they crunched the numbers, they discovered that changes in the policy rate explain only about 3 to 4 percent of the ups and downs in stock prices over the next year. In fact, once they accounted for all the noise and uncertainty, they couldn't even find a reliable cause-and-effect link between the policy rate and the stock market. The paper explicitly rules out the idea that the policy rate is the main driver of stock returns in Ghana; it suggests that the market is simply too small and too focused on a few big companies for the standard "discount rate" rule to work cleanly.

So, if the policy rate isn't the main chef, who is? The study found two other "flavors" that actually season the market, depending on the mood. First, when the market is in a happy, bullish mood (the top 25% of performance days), global oil prices are the star ingredient. Since Ghana produces oil, when global oil prices shoot up, the whole market gets excited, but only when things are already going well. Second, when the market is in a scary, bearish mood (the bottom 25% of performance days), the short-term Treasury bill rate becomes the most important factor. This is like a funding cost that only bites the financial sector hard when the kitchen is already on fire. The researchers also found that the connection between the policy rate and stocks actually gets stronger the longer you wait to look, rather than peaking in the middle, which is different from what we see in bigger, more mature economies.

In the end, the paper suggests that for investors and policymakers in Ghana, watching the policy rate alone is like watching a clock that stopped ticking. Instead, they should keep a closer eye on global oil prices when the market is soaring and on short-term funding costs when the market is panicking. The study doesn't claim to have solved the mystery of the Ghanaian market, but it does provide a clear, data-backed map showing that the usual rules of the road don't quite apply here. The market is loosely coupled to the policy rate, and its true heartbeat is driven more by global commodities and immediate funding stress than by the central bank's main dial.

Technical Summary: Monetary Policy, Exchange Rate Shocks, and Asset Prices in a Small Open Frontier Economy

Problem and Motivation
The transmission of monetary policy to asset prices is a well-established mechanism in advanced economies, yet its operation in frontier markets like Ghana remains empirically unsettled. Frontier equity markets are characterized by thin trading, limited institutional participation, and monetary regimes that have oscillated between disinflation, easing, and exchange-rate stabilization. A critical methodological gap in prior Ghana-specific literature is the blending of index series with incompatible construction methodologies (e.g., pre- and post-2011 index structures), which introduces spurious structural breaks unrelated to monetary policy. Furthermore, theoretical ambiguity exists regarding the sign of policy rate effects: while higher rates may lower valuations via discount rates, they may simultaneously support risk appetite by signaling currency stabilization. The study addresses whether monetary policy shocks transmit to equity returns in Ghana uniformly across the return distribution and time, or if the relationship is state-dependent and driven by other macro-financial factors.

Methodology
The study employs an integrated multi-method framework analyzing monthly data from January 2014 to December 2024 ( $N=131$ usable return observations). The sample is restricted to the current-regime Ghana Stock Exchange Composite Index (GSE-CI) and Financial Stock Index (GSE-FSI) to ensure structural consistency.

The econometric approach combines five distinct techniques:

Unit Root and Structural Break Testing: Augmented Dickey-Fuller (ADF) and Zivot-Andrews (ZA) tests are used to determine integration orders, accounting for endogenous structural breaks (e.g., the 2022–2023 debt restructuring).
Causality Analysis: The Toda-Yamamoto augmented-VAR procedure is applied to test Granger-causal linkages without pre-testing for cointegration, ensuring robustness to uncertain integration orders.
Distributional Analysis: Bayesian Quantile Regression (BQR) with Bayesian Model Averaging (BMA) estimates the response of equity returns to shocks across eight quantiles ( $\tau = 0.05$ to $0.90$). This approach formally accounts for model uncertainty regarding which predictors belong in the model at specific quantiles, reporting Marginal Posterior Inclusion Probabilities (MPIP).
Dynamic Importance: Structural Vector Autoregression (SVAR) with Cholesky decomposition provides orthogonalized impulse responses and Forecast Error Variance Decomposition (FEVD) to quantify the share of variance in equity returns attributable to monetary shocks versus other macro-financial shocks (oil, exchange rates, inflation, money supply).
Time-Frequency Analysis: Continuous Morlet wavelet coherence analysis examines how the co-movement between policy shocks and equity returns varies across short (1–6 months), medium (6–18 months), and long (18–36 months) horizons.

Key Results
The empirical findings present a more modest role for domestic monetary policy than often assumed in advanced-economy literature:

Policy Rate Insignificance: Across all methods, the domestic policy rate (MPR) shows no robust Granger-causal relationship with either the GSE-CI or GSE-FSI. In Bayesian quantile regressions, the MPR exhibits weak posterior support (MPIP < 0.35) for inclusion at any quantile. FEVD indicates that policy rate shocks explain only 3–4% of the twelve-month-ahead forecast error variance for equity returns.
Oil Price Dominance (GSE-CI): Global oil price shocks demonstrate strong, quantile-dependent explanatory power for the Composite Index. Specifically, oil prices show "very strong" posterior inclusion probabilities (MPIP > 0.93) at upper (bullish) quantiles ( $\tau \geq 0.75$ ), suggesting that global commodity prices drive the market's best-performing states, consistent with Ghana's status as an oil producer.
Funding Cost Sensitivity (GSE-FSI): For the Financial Stock Index, short-term Treasury bill rates (TBR) are the dominant predictor, but only at lower (bearish) quantiles. The TBR shows "very strong" inclusion probability (MPIP > 0.95) at $\tau = 0.05$ and $0.10$, indicating that funding costs are critical specifically during financial-sector stress states.
Wavelet Coherence: Contrary to the notion of a medium-run "sweet spot," coherence between policy shocks and the GSE-CI strengthens as the horizon lengthens (rising from 0.264 in the short run to 0.452 in the long run). For the GSE-FSI, coherence is weakest in the medium run but intensifies during crisis periods (2014–2016 and 2022–2023).
Causality: The only robust causal link identified is from money-supply growth to the GSE-CI. No other macro-financial variable shows a statistically significant causal relationship with the indices under the Toda-Yamamoto framework, except for a contemporaneous correlation between TBR and GSE-FSI.

Significance and Claims
The paper claims to provide the first distributional, multi-horizon evidence that Ghana's equity market is only loosely and unevenly coupled to the domestic policy rate. The authors argue that the market is too thin and dominated by idiosyncratic liquidity events for the policy rate to leave a consistent fingerprint on aggregate index returns.

Instead, the study identifies two more policy-relevant channels:

Global Commodity Prices: For the broad market, global oil prices are a primary driver of bullish sentiment, acting as a distinct risk factor from domestic monetary policy.
Short-Term Funding Costs: For the financial sector, short-term rates matter most during stress episodes, a nuance invisible to mean-regression models.

The authors conclude that for policymakers, investors, and regulators in Ghana, monitoring global commodity prices and short-term funding costs offers greater diagnostic value than the policy rate in isolation. The findings caution against treating the policy rate as a reliable lever for managing equity market conditions in this frontier setting, suggesting that transmission depends heavily on market depth and credibility, which remain constrained in Ghana.

Technical Summary: Monetary Policy, Exchange Rate Shocks, and Asset Prices in a Small Open Frontier Economy

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