It Is a Good Idea to Measure How Your products sell. Not only in terms of number of items sold, but rather where your profit/margin is. If you decide to introduce a new product, you can test how it sells by measuring the number of orders. If it proves to sell well and if you can offer it at a satisfactory profit, you can stock up more of that particular product. Remember that you have to measure a long enough period of time to get a good idea of how your products sell.