Rolled Throughput Yield

Also known as RTY · rolled yield · first pass yield chain · hidden factory · cumulative yield · yield through n steps

RTY=y n\mathit{RTY} = y^{\,n}
steps

Worked example: five steps at 99% each → 95.099% rolled yield — press Try an example to run it live, then adjust anything.

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Rolled Throughput Yield explained

yyyRTYn

Rolled throughput yield is what actually gets through a chain of steps with no rework at all: yny^n when every step has the same first-pass yield. Five steps at 99% each is not 99% and not 95% by subtraction, it is 0.995=0.9510.99^5 = 0.951. 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 0.951/12=0.99570.95^{1/12} = 0.9957, 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 formula

RTY=y n\mathit{RTY} = y^{\,n}
Where
  • RTY\mathit{RTY}= Rolled throughput yield
  • yy= First-pass yield of each step
  • nn= Number of steps (steps)

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