A 1913 formula still tells warehouses exactly how much stock to order

Ordering too little stock means constant reordering costs; ordering too much ties up cash in a warehouse. Ford W. Harris's 1913 'economic order quantity' formula calculates the exact batch size that minimises the combined cost of ordering and holding inventory — a simple square-root equation still taught in every operations-management course and built into modern supply-chain software.

— Ford W. Harris, How Many Parts to Make at Once — Factory, The Magazine of Management, 1913