The larger agencies also come into intimate contact with experts

in every department of business. Their clients are usually dominating concerns. So they see the results of countless methods and polices.They become a clearing house for every thing pertaining to merchandising. Nearly every selling question which arises in business is accurately answered by many experiences.

Under these conditions, where they long exist, advertising and

merchandising become exact sciences. Every course is charted. The compass of accurate knowledge directs the shortest, safest, cheapest course to any destination.

We learn the principles and prove them by repeated tests. This is

done through keyed advertising, by traced returns, largely by the use of coupons. We compare one way with many others, backward and forward, and record the results. When one method invariably proves best, that method becomes a fixed principle.

Mail order advertising is traced down to the fraction of a penny.

The cost per reply and cost per dollar of sale show up with utter

exactness.

One ad is compared with another, one method with another.

Headlines, settings, sizes, arguments and pictures are compared. To reduce the cost of results even one per cent means much in some mail order advertising. So no guesswork is permitted. One must know what is best. Thus mail order advertising first established many of our basic laws.

In lines where direct returns are impossible we compare one town

with another. Scores of methods may be compared in this way,

measured by cost of sales. But the most common way is by use of the coupon. We offer a sample, a book, a free package, or something to induce direct replies.