Rolled Throughput Yield
Also known as RTY · rolled yield · first pass yield chain · hidden factory · cumulative yield · yield through n steps
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Learning zone
Rolled throughput yield is what actually gets through a chain of steps with no rework at all: when every step has the same first-pass yield. Five steps at 99% each is not 99% and not 95% by subtraction, it is . One unit in twenty is touched twice somewhere along the way.
Extend it and the arithmetic turns unforgiving. Twenty steps at 99% is 81.8%. Fifty steps at 99% is 60.5%. This is why long processes with individually impressive stations still disappoint, and why the phrase "hidden factory" was coined: the rework loops that produce the difference between 100% and RTY are staffed, floored and paid for, but they appear on no process map because each one is small.
Turn the formula around and it becomes a specification tool. To hold 95% overall across twelve steps, each step needs , so 99.57% per step. Anyone who has quoted a 95% target on a twelve-step process without doing that division has promised something quite different from what they think.
- = Rolled throughput yield
- = First-pass yield of each step
- = Number of steps (steps)
- Rolled throughput yield — Safety Stock (Statistical Buffer), Inventory Turnover Ratio
- First-pass yield of each step — Safety Stock (Statistical Buffer), Inventory Turnover Ratio
- Number of steps — Economic Order Quantity (Wilson EOQ), Reorder Point