Want to go deeper? Use Excel, Python ( statsmodels ), or R for advanced decomposition (additive or multiplicative).
Here’s a clear, professional post you can use for LinkedIn, a blog, or a social media update: how to find seasonal index
Find the average value for each season (e.g., average of all Januaries). Want to go deeper
Collect at least 3–5 years of data for the same period (e.g., monthly or quarterly). Want to go deeper? Use Excel
Seasonal indices help you uncover repeating patterns in your data — whether it’s sales, web traffic, or demand. Here’s how to calculate them step by step:
Calculate the grand mean of all data points across all periods.