Mistake-proofing eliminates most traditional inspection, substantially reducing the delay between production steps. Operators also spend less time examining their work to make sure it is correct. Additionally, interruptions for handling scrap, rework, and repair are eliminated. Finally, the "guided completion" afforded by mistake-proofing can significantly reduce decision times in complex operations. Some organizations have reported that mistake-proofing has doubled productivity.

Only mistake-proofing and 100% inspection techniques can produce and sustain defect rates below 50 parts per million (ppm). For comparison, defect rates in the highest performing companies that are aggressively working on 6 Sigma typically exceed 1000 ppm. In other words, defect rates with other traditional techniques are 20 to 100 times greater than achievable with mistake-proofing.

Shigeo Shingo, the quality guru that lead the quality revolution at Toyota, stated: "This (mistake-proofing), I think, is the quickest road leading to attainment of zero defects." Toyota’s experience and the experience of organizations that have followed the Toyota production model have repeatedly demonstrated that Shingo’s assessment is correct. The figure below illustrates De-Sta-Co’s experience with mistake-proofing.

Surprisingly, customer loyalty is not the strongest driver for implementing mistake-proofing. As production efficiency improves, manufacturers become increasingly aware of the fact that a single defect in the process shuts down the production flow. The desire to eliminate undesirable production shutdowns is the strongest incentive for eliminating defects and implementing mistake-proofing. Uninterrupted production flow can not be achieved without mistake-proofing.

In contrast to most auto manufacturers, Toyota has virtually no rework areas in their assembly plants. Handling scrap, or performing rework and repair are only necessary because the work was not done correctly the first time. Collectively, these activities represent wasted effort that can be avoided or eliminated.

In spite of the fact that mistake-proofing requires many devices to be effective, the cost of quality control using mistake-proofing is substantially less expensive than traditional alternatives. In addition to eliminating most of the inspection time, collectively mistake-proofing devices can be dramatically less expensive than the Coordinate Measuring Machines (CMM) machines or custom gauges that would be required otherwise.

When every part is virtually defect free, there is no need for piles of parts between work stations. This contributes to dramatic reductions in in-process parts and materials - allowing manufacturer’s to shrink the factory floor. Illustrating the benefit of shrinking inventory, the NUMMI plant in Fremont, California, which is operated by Toyota, produces three different vehicles (Corrollas, Chevy Prisms, and Tacoma trucks) in the same facility where GM formerly produced a single type of vehicle.

When customer’s receive defect free products, they’re happy. Experience shows that customers of the companies with the highest quality are loyal. In addition, customers are willing to pay a premium for higher quality.