What is hierarchical time series forecasting and where is it used?

Hierarchical forecasting models time series at multiple aggregation levels and ensures consistency across levels.

Hierarchical time series involve structured aggregation levels, such as country → state → city sales. Forecasts must be consistent across levels. Techniques like bottom-up, top-down, and reconciliation methods (e.g., MinT) ensure coherence. This is critical in enterprise forecasting systems.