The difficulty of determining and maintaining accurate standards of performance is one of the principle causes of the erosion of the payment-by-results system. Once inconsistencies are maintained the erosion becomes more severe. Average bonus earnings drift upwards beyond those originally expected or output falls well below that attainable; adherence to customary norms becomes subject to strict informal work group discipline; inequities in effort/bargain relations give rise to continuing disputes and leap-frogging wage claims; and illicit administrative practices proliferate.