A backlog is the aggregate sale value of all received customer orders that have not yet been shipped. A backlog is present when the production capacity of a business is less than the rate at which orders are being received. The trend line of the backlog can be monitored to see if it changes over time. An increasing backlog indicates a substantial order book that will eventually translate into future sales, or a decline in production capacity. A declining backlog either indicates that there will eventually be a drop in sales, or that the production capacity of the business has increased.