Which one of the following is not one of the factors that affect the $\frac{S}{Q}$ rating of a company's footwear?

The percentage use of overtime labor at a given facility

Current$-$year spending per footwear model for new styling$/$features

Current$-$year and cumulative expenditures to train workers in using the best practices to assemble athletic footwear.

Current$-$year expenditures for Total Quality Management

$($TQM$)$ and$/$or Six Sigma quality control programs

The percentage use of superior materials