Beginning the first week of January 2013, point-of-sale data from over 4,000 Walmart locations across the U.S. and Puerto Rico will be added to the 12,000 locations that currently report their sales to Nielsen BookScan U.S.

Nielsen BookScan, which monitors the English-language book industry worldwide, will now represent over 80% of the retail print book marketplace in the U.S.

“BookScan’s integration of Walmart data will reinforce the importance of business information and analytics to everyone connected to the book business,” said Jonathan Stolper, v-p & general manager, Nielsen BookScan. “Comprehensive point-of-sale information is essential for good publishing, sales, marketing, and supply chain decision making. Greater accuracy of information and insight into book consumers is what all BookScan clients want, and adding Walmart data provides a big and long-awaited step in that direction.”

The agreement with Walmart will not include historical print unit sales and will not include