The value of control kind of internal information lay more in showing when, and in which direction, prices should be changed rather than by what amount. Information provided, either in control accounts or on an ad hoc basis, helped decisions to be made on stock levels, material purchases, and advertising outlays and on pricing. If extra information was sought for pricing, it usually came from the management accountants. Some of the information provided to managers for control purposes could also be used for less-routine decisions. Even where firms had intricate systems for calculating costs, arithmetic manipulation seemed to play a bigger role than rigorous, logical thought. With average costing, it would have been difficult, even impossible, for the manager to decide which were fixed and which variable costs. Cost becomes, within limits. However, relevant costs are what managers need to know, and relevant costs are almost always marginal costs of one kind or another.