Quantifying Inter-Annual Seasonal Drift in Tomato Prices Using Dynamic Time Warping: Evidence from Kolar Market

TL;DR

This study uses Dynamic Time Warping to analyze inter-annual variability in tomato prices in Kolar, revealing that seasonal patterns recur but vary significantly across years, impacting forecasting models.

Contribution

It introduces DTW as a tool to quantify temporal shifts in seasonal price patterns, highlighting the need for adaptive forecasting in volatile markets.

Findings

2022-2023 had the highest pattern alignment despite price spikes

2021-2022 showed the weakest alignment, indicating structural shifts

Seasonal patterns recur but with significant temporal variability

Abstract

Tomato prices in Kolar market exhibit high volatility alongside recurring seasonal patterns, but the consistency of these patterns across years remains unclear. This study analysed weekly tomato prices and arrivals from 2010-2024 to quantify inter-annual variability using descriptive statistics, seasonal indices, and Dynamic Time Warping (DTW). Descriptive analysis confirmed extreme fluctuations (CV = 77% for prices, 102% for arrivals) with positive skewness and heavy tails, indicating frequent extreme events. Seasonal indices revealed recurring intra-year cycles, but year-to-year alignment varied substantially. DTW analysis for 2021-2024 quantified pattern similarity, showing that 2022-2023 had the highest alignment (DTW distance: 23,258) despite extreme price spikes, whereas 2021-2022 exhibited the weakest alignment (distance: 39,049), reflecting structural shifts in market dynamics. Path length metrics indicated minimal temporal warping in 2022-2023 (71 points) versus extensive alignment in 2021-2022 (83 points). These results demonstrate that while seasonal patterns recur, their temporal consistency is not fixed, highlighting the need for forecasting models that adapt to both magnitude volatility and temporal shifts. The study also illustrates the utility of DTW for agricultural price analysis and the limitations of relying solely on fixed seasonal patterns in volatile commodity markets.