Abandonment rate is a term associated with the use of virtual shopping carts. Although shoppers in brick-and-mortar stores rarely abandon their carts, abandonment of virtual shopping carts is quite common. Marketers can count how many of the shopping carts used in a specified time period result in completed sales versus how many are abandoned.
The abandonment rate is the ratio of the number of abandoned shopping carts to the number of initiated transactions.
E-commerce shopping cart abandonment rates are tracked regularly by the Baymard Institute. 
Abandonment rate helps marketers understand website user behavior. Specifically, abandonment rate is defined as “the percentage of shopping carts that are abandoned” prior to the completion of the purchase.
As an example, an online comics retailer found that of the 25,000 customers who loaded items into their electronic baskets, only 5,000 actually purchased:
- Purchases not completed = purchases initiated less purchases completed = 25,000 – 5,000 = 20,000.
- Abandonment rate = Not completed / Customer initiation = 20,000 / 25,000 = 80% abandonment rate.