Last time, I wrote that the key to successful direct marketing is to find an optimal combination of reach and frequency-putting your message in front of the right audience size the right number of times. This column will provide the conceptual framework for improving the accuracy of your marketing efforts. I'm going to show you how to quantify the best possible return on your investment of both time and marketing dollars. In other words, you're going to learn the way to get the most people in the seats for your program at the lowest cost per attendee.

In the third and final column of this series, we'll put numbers into a formula-based on the concepts discussed here-that will help you unearth those prospects who are not only most likely to attend your programs, but to become long-term customers.

First we must acknowledge a well-documented business principle: less than 20 percent of customers account for 80 percent of sales and 150 percent of profits. And yes, promoting lifelong learning to healthcare professionals is a business like any other when it come to the "80/20 Rule." Check your own data and I'm confident you'll find that 80 percent of your registrants will come from 20 percent of your mailing list. The method for identifying and extracting the most value from that 20 percent is called database marketing.