This table gives the number of retail (sell-through) Blu-ray Disc (BD) units shipped to trade in every territory covered by Video Intelligence for which data is available. Data is net of returns and reflects stock keeping units (SKUs) rather than actual discs so each unit may contain more than one disc. In the early years of a format?s development, the number of BD retail units shipped to trade usually exceeds the number of retail units sold, as retailers and wholesalers fill the pipeline and expand shelf space. In a mature market sales and shipments tend to be similar while as a format reaches the end of its life sales may exceed shipments as retailers stop replacing all sold stock and thus reduce the shelf space available.