That means that after twenty days, they have received half of the orders that they are going to get from that particular catalog. They can track the entire success of a book by sales made during the first 20 days. This is powerful knowledge. The power comes from the fact that you can conduct extremely rapid tests. In the example given above, if the marketer knew his half-life day, he could know after three or four weeks which offer was the most profitable, and could launch his million household rollout months earlier.
Time is money, and half-life saves time.
At the Database Marketing Institute half-life theory has been taught for some time. Institute staff has have worked with some participating companies to discover how it works in their situations. Half-life computation is often tedious work. For this reason, the Institute developed added a half-life computation model which it added to its standard RFM software. They applied this module to some of the participant's promotion responses with interesting results.