Accuracy is of prime importance in the making of an estimate, for it would profit a man nothing to be awarded all the work he figures on, only to find that he has lost money on every contract. Conversely, as an estimator's time is of value, it is a waste of money to estimate daily on work only to lose on account of inaccuracies either in the taking off of items or in calculating the cost of materials. Where plans and specifications are full and complete, and nothing is ambiguous or left to conjecture, the net cost for doing the work should vary but very little among the different contractors estimating on an operation. If they are all equally careful in taking off quantities their several items ought to tally so far as amounts are concerned, and whatever difference there would be in the cost of the various items would arise from the different prices paid for the goods, according as one is a good or bad buyer. The only chance for difference of opinion as to cost will lie in the enterprise and originality or lack of enterprise or originality of the several estimators, and in the computation of the cost of labor. Here again the difference will rise according to the ability of the contractor to select good men and use them advantageously.

On work which is estimated upon, but lost, no record can be kept to show how accurate was the list of materials and the prices allowed. On work contracted for, however, a careful record should be kept, showing the actual cost and the estimated cost of the various items. This information is invaluable to a careful business man. Profit, but only a fair profit, should be made on every item entering into a plumbing contract, and if a loss is experienced instead of a profit the contractor wants to know of the loss and the cause, so he can adopt measures to prevent a repetition. For instance, if the record shows that the quantity of soil pipe estimated on was correct but the pipe cost more than allowed for, that would indicate that something was wrong, with his prices. Investigation might show that the latest quotation, or discount, had not been entered in the cost book, and that consequently he was selling soil pipe at an old price and buying it at a later and higher one. Such information would not be available if it were not for keeping record of all items and checking them up. At all events, the cause of the loss would be ascertained, and the cause eliminated. If, instead of the materials, the items of labor should show a loss it should lead to an investigation of the cause and a revision of the manner of estimating the cost of labor. If an inspection of the personnel of his workmen shows that some are below the average in skill or speed, the remedy obviously would be to replace them with good workmen who could do an average day's labor. If, however, the workmen are up to the average and are doing a fair day's work it would be necessary when estimating on future work to allow less for an actual day's labor.

No less necessary is it to check up and analyze the cause of excess profit on the various items. Each item of actual cost ought to correspond approximately to the estimated cost, and when there is a large balance in favor of the contractor, if he be a careful business man, he will want to know the reason why. If in many of his items the actual cost runs much below the estimated cost he may assume that having the contract awarded to him was more the result of an accident than due to careful business methods and accurate estimating. An estimator should feel as deeply humiliated to have his estimates constantly run above the actual cost as to have them run below, for in either case the discrepancy is due to carelessness, or to ignorance of conditions with which he should be familiar The careful estimator will try-to ascertain the exact amount the labor and material will cost him, then, knowing what percentage he wishes to make on that work, he can easily add the profit. If, after carefully estimating the work, he is underbid and his competitor makes a profit on the contract he knows something is wrong with his prices. He is paying too much for material; his labor is running too high; he has not laid out the work in the building in the most economical way to economize labor and material, or some other condition is against him and that condition must be discovered and overcome before he can succeed.