ResearchResearch paperTraining & Scaling · Large Language Models · Evaluation & Benchmarks1 source · Oct 6, 2026

Are We Really Benchmarking Forecasting Models? The Impact of Preprocessing on Time Series Performance

We study this effect through a preprocessing-aware benchmark that evaluates 11 forecasting models across 16 reversible preprocessing pipelines on 29,000 M4 time series.

Key points

  • While established literature underscores the pivotal role of preprocessing in forecasting accuracy, this stage remains largely overlooked in current research.
  • Modern benchmarks typically resort to simple scaling, failing to account for critical transformations required to address nonstationarity, such as differencing.
  • This omission creates a significant structural preprocessing bias that favors models with built-in data treatments while obscuring the true potential of simpler architectures.
  • Our results identify preprocessing as a key driver of forecasting performance.

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