A week back an article in NYTimes discussed the math's behind Groupon and the parameters you need to be watchful of to make sense of Groupon.

NYT - Doing the Math on a Groupon Deal

Groupon is advertising. If you don’t need or believe in advertising, there is no reason to look at this. It costs money. Instead of writing a check for an ad, you are choosing to lose money on sales. This can wreak havoc on the brain cells of a good retailer who is always watching profit margins. It can feel wrong, especially when the coupon customers don’t spend more than the amount of the coupon.

Eight key calculations:

1. Your incremental cost of sales — that is, the actual cost percentage for a new customer. If you are giving boat tours and have empty seats, your incremental costs for an additional customer are next to nothing. If you are selling clothes, your incremental costs might be 50 percent of the sale price. Food might be 40 percent. In any case, don’t include fixed costs that you would be incurring any way.

2. The amount of the average sale. If the coupon is for $75, will the customers spend more that that? I have seen more than one retailer complain that nobody spends more than the value of the coupon. That’s unlikely but I am sure it can feel that way, and that is my point: Keep track.

3. Redemption percentage. You don’t really know until the end, but from my experience and from what I have heard, 85 percent is a good guess.

4. Percentage of your coupon users who are already your customers. I’m sure this number varies tremendously depending on the size of your city, how long you have been around, and the type of business.

5. How many coupons does each customer buy? (The more they buy, the fewer people are exposed to your product or service.)

6. What percentage of coupon customers will turn into regular customers? Again, it can seem as if they are all bargain shoppers who will never return without a discount, but that’s almost impossible. Is it possible 90 percent won’t return? Sure.

7. What is the advertising value of having your business promoted to 900,000 people — that’s the number on Groupon’s Chicago list — even if they don’t buy a coupon?

8. How much does it normally cost you to acquire a customer through advertising? Everything is relative.