There are a variety of metrics that may be applied to determine if the list or lists you are considering are large enough to meet your goals for revenue generation. Among them is the average response rate for
your category, the total sales you need to break even and the ability you have of identifying your likely target.
Care must be taken to avoid mailing to a list that is too large. Nothing aggravates customers who have taken the trouble to respond more, than being told something is unavailable or back-ordered. Unless what you have to sell is absolutely unique, you've just created awareness for your competition, and maybe even a sale.
