Since, therefore, real income, in terms of product, may be incapable of precise numerical measurement, it is often convenient to regard income in terms of wage-units (Yw) as an adequate working index of changes in real income.

因此，由于以产品表示的实际收入可能无法进行精确的数值测量，因此将以工资单位 (Yw) 表示的收入视为实际收入变化的适当工作指标通常很方便。