Fuente: Wipo "digitalization" Methods, systems, and apparatuses are provided for determining digital book sales. A plurality of digital book data for a plurality of digital book titles for a period and associated with a plurality of retailers may be received by one or more computing devices. A sales rank may be determined for the plurality of digital book titles for each retailer. A weighted unit sales amount may be determined for each digital book title of the plurality of digital book titles for each retailer. An optimal curve fit of the sales rank to the weighted unit sales amount may be determined for each digital book title of the plurality of digital book titles for each retailer. A period unit sales amount may be determined for each digital book title for the plurality of retailers.