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Leveraging Large Language Models for Indonesian Retail Sales Probabilistic Forecasting

Keywords:
Time Series Forecasting, Chronos, Large Language Models, AutoGluon, Retail Sales Index, Probabilistic Forecasting, Indonesia
Abstract

This research evaluates the effectiveness of Large Language Models (LLMs) for probabilistic forecasting of the Indonesian Retail Sales Index. We analyze monthly retail sales index data from Bank Indonesia, spanning January 2012 to January 2025 across seven product categories. A broad spectrum of time series forecasting models is developed using AutoGluon Time Series, including a baseline seasonal naive model, machine learning-based tabular models, classical statistical models (AutoETS, Dynamic Optimized Theta, and NPTS), deep learning models (Temporal Fusion Transformers, PatchTST, TiDE, and DeepAR), and transformer-based LLMs from the Chronos and Chronos Bolt families. For the LLM models, we consider both zero-shot forecasting (direct application of pretrained models) and fine-tuning on the historical retail data. All models are evaluated on a hold-out test period using seven metrics: Scaled Quantile Loss (SQL), Weighted Quantile Loss (WQL), Mean Absolute Error (MAE), Mean Squared Error (MSE), Root Mean Squared Error (RMSE), Mean Absolute Percentage Error (MAPE), and Symmetric MAPE (SMAPE). The fine-tuned Chronos [base] model achieved the best overall performance, yielding the lowest errors with SQL = 0.274, WQL = 0.136, MAE = 0.184, MAPE = 0.267, MSE = 0.059, RMSE = 0.243, and SMAPE = 0.218. These results highlight the potential of LLM-based models to improve the accuracy of retail sales forecasts in Indonesia, especially in capturing long term trends, while underscoring the remaining challenges in modeling short-term fluctuations.

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Forecast vs. Actuals for Each Retail Category using Fine-Tuned Chronos [base]
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2026-05-16
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Copyright (c) 2026 M Dzaky Efendi, Salhazan Nasution, Mondheera Pituxcoosuvarn (Author)

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How to Cite

[1]
M. D. Efendi, S. Nasution, and M. Pituxcoosuvarn, “Leveraging Large Language Models for Indonesian Retail Sales Probabilistic Forecasting”, Artif. Intell. Lang. Models, vol. 1, no. 1, pp. 1–18, May 2026, Accessed: May 27, 2026. [Online]. Available: https://acspub.id/index.php/ailm/article/view/2

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