Wal-Mart Stores is finally going to allow market researchers to use data on the sales of video games at Walmart and Sam’s Club warehouse stores, according to AdAge.

That breaks a 10-year ban on sharing data for Wal-Mart Stores, which previously considered that data to be a company secret. By allowing the data dump for Nielsen and NPD, Wal-Mart will finally be a good citizen in helping analysts gauge the size of the video game business. Not only will Wal-Mart share game data, it will also share other retail data as well.

Nielsen will be able to provide clients access to to Wal-Mart and Sam’s Club store data in “a few months,” said Nielsen spokeswoman Jennifer Frighetto. “We’re raring to go,” she said to AdAge, “and starting to work with [Wal-Mart] and train them and we will be providing new views of our U.S. industry numbers. It’s a big impact.”

NPD has had to rely on its own estimates for game sales at Wal-Mart stores for a decade. That’s been a problem because Wal-Mart is believed to have as much as 20 percent of the market share in the retail game sales industry. That left a gaping hole in the data, leaving the market analysts and the game publishers driving blind when it came to total industry sales.

The NPD data — or lack of it — has been a sore point for some time. The stock prices of game companies have risen or fallen based on the monthly NPD game data. That data often shows that the game industry is shrinking, even though there are expanding parts of the industry that aren’t measured precisely every month. Social games, rentals, mobile games, tablet games, and online games are left out of the retail sales data, which is shrinking these days. That makes investors think the game business is contracting.

The new data will include census data from all U.S. Wal-Mart stores, Neighborhood Markets and Sam’s Clubs, and it will include historical data, Frighetto said.

AdAge said the executive who made the change is Cindy Davis, the former Sam’s Club chief marketer who earlier this year became executive vice president of Wal-Mart global consumer insights. Davis said the sharing of the data will lead to deeper insights into customer purchasing and category growth.