Every manufacturing process has a mode of operation that produces the greatest value at the lowest cost. Any phenomenon that disrupts the operation by reducing value or increasing costs is known as variance. Efficiency systems provide precise information about variance, which in the papermaker's world includes the mechanical and process disturbances that cause production losses, speed limitations, broke, or poor sheet quality. Efficiency systems gather information about process variation from sensors (pressure transducers, accelerometers, optical sensors) that are permanently installed on the paper machine, from the stock-approach system to the reel. Signals from these units are relayed to a computer, which relates the process variations to the measured variations in paper quality (basis weight, moisture content, gloss, formation, opacity) from the paper machine's gauging systems. The computer pinpoints the individual contribution of a paper-machine component (fan pump, headbox pulsation, roll corrugation, felt vibration) and correlates it with variations in paper quality. Such information can increase system availability, reduce maintenance costs, and improve product quality.