How Spreadsheets Quietly Cost Supply Chains Millions

A simulation comparing spreadsheet-based supply chain planning against a connected platform (SupPlan) using a fictional fashion retailer, SupFashion. In the spreadsheet scenario, a 50-unit forecast adjustment for a marketing campaign takes 14+ days to reach all planning teams, causing missed factory lead times and empty shelves. With the integrated platform, the same change cascades across demand, merchandising, supply, and distribution teams in a single working day, preserving the 52-day factory lead time and ensuring stores are stocked before the campaign starts. The author built SupPlan as an open-source simulation environment for testing integrated business planning algorithms, with plans to add distribution and financial modules.