The shopping cart can tell retailers a great deal about the performance of the eCommerce site, but abandonment rates are only part of the story. In order to see the bigger picture, retailers need to look at other metrics.
Ideally, ecommerce performance would be judged by the visitor and not by the session. That is, customers often visit a site multiple times before buying. With each visit, they become more likely to buy. Abandonment rates and most other web analytics, however, look at the session level, or sometimes over a fixed period of time. Read the rest at eMarketer.