Darwin Chapuswike

Building a Zambia Copper Prices Forecast Tool: Predicting Future Trends

April 6, 2025

In March 2025, I embarked on an exciting project to develop a Zambia Copper Prices Forecast Tool, designed to predict future copper prices in both USD and ZMW, as well as forecast the ZMW/USD exchange rate. As an L2 Support Engineer at NetOne Zambia, I have always been passionate about leveraging technology to solve real-world problems, and this tool is a step toward providing valuable economic insights for Zambia, a country where copper is a cornerstone of the economy.

The tool, which I developed using Python and Streamlit, allows users to upload historical data for copper prices (in USD/lb) and ZMW/USD exchange rates, then forecasts prices and rates for up to 30 days beyond March 28, 2025, the last date in the dataset. It is a practical solution for stakeholders in Zambia’s mining sector, helping them anticipate market trends and make informed decisions. You can try the tool yourself at copper-prices-forecast-zm.streamlit.app.

The development process involved several key steps. First, I used Streamlit to create an interactive web app where users can upload two Excel files: copper_fallback.xlsx for copper prices and zm_fallback.xlsx for exchange rates. Both files must contain a Date column (in YYYY-MM-DD format) and a Close column (for the closing price or rate). The app aligns the data by date, ensuring that copper prices and exchange rates match up, for example, the exchange rate on 28/03/2025 was 28.6817 ZMW/USD.

The forecasting logic is based on a simple yet effective trend analysis. Here is how it works:

• Data Alignment: The app matches copper prices and exchange rates by date, creating a unified dataset. If there are no matching dates, it throws an error to ensure data integrity.
• Historical Trends: It calculates the average of the last three data points (a 3-day moving average) for both copper prices and exchange rates to establish a baseline.
• Rate Trend: The app computes the percentage change in the exchange rate between the last two days (e.g., 27/03/2025 to 28/03/2025) to determine the trend direction, whether the ZMW is appreciating or depreciating against the USD.
• Forecasting: For each forecast day, the app adjusts the baseline price and rate by the rate trend, scaled by the number of days into the future. For example, if the exchange rate is increasing by 1% per day, the forecasted rate for day 2 would be the baseline rate multiplied by (1 + 0.01 * 2). Copper prices in USD are adjusted similarly, and ZMW prices are calculated by multiplying the USD price by the forecasted exchange rate.
• Visualization: Using Plotly, the app displays historical and forecasted prices on a dual-axis chart, with USD/lb on the left axis and ZMW/lb on the right, making it easy to see trends.

The tool is user-friendly, with detailed instructions on how to format and upload data, including where to source historical data (e.g., MacroTrends for copper prices, Yahoo Finance for exchange rates). It also validates the data, ensuring the last date is 28/03/2025 and that there are enough data points (at least 3) for forecasting. The result is a practical tool that provides actionable insights for Zambia’s copper industry, reflecting my commitment to using tech for economic impact.