How do I interpret and improve Days Inventory Outstanding?

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AcadiFi · Accepted Answer

Days Inventory Outstanding equals average inventory divided by cost of goods sold per day, or 365 * (Inventory / COGS). It measures how many days of sales a company's inventory represents. Rising DIO without proportionate demand growth is usually a warning sign.

Step one: decompose inventory. Separate raw materials, work-in-process, and finished goods. A raw materials buildup might reflect strategic stockpiling or supply chain caution. Work-in-process growth could signal production bottlenecks. Finished goods buildup is usually the most concerning: it may indicate weak demand, channel stuffing, or slow-moving SKUs.

Step two: compare against category dynamics. Compute inventory turnover (COGS / avg inventory) by product line. If sporting goods turns 8x but apparel has dropped to 3x, apparel is the problem area. Age the inventory: stock over 180 days should be scrutinized for obsolescence reserves.

Step three: audit demand forecasts. If actual sales consistently undershoot plan, production is over-ordering. Review the sales and operations planning process.

Step four: examine accounting effects. LIFO-to-FIFO conversions or cost capitalization changes can distort comparisons. Look at the inventory footnote for obsolescence reserves and write-downs.

Imagine Lionel Cabrera analyzing Wembleton Electronics. DIO rose from 45 to 72 days. Drilling in, finished goods of discontinued smart-home products grew from $8M to $34M. Management had continued manufacturing despite declining demand. Cabrera models a $26M write-down and reduces forward earnings forecasts.

Improvement tactics: demand-driven replenishment, SKU pruning, markdown strategies for aged stock, and tighter production-planning controls. Monitor progress with weekly DIO by category, not just consolidated quarterly numbers.

How do I interpret and improve Days Inventory Outstanding?

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