Store brands are gaining market share against the big national brands in America’s fastest growing retail channels, according to Nielsen’s latest sales statistics.

For the 52 week period that ended Dec. 24, 2016, retailers’ brands strongly outperformed the national brands in the rapidly-growing mass merchandisers segment of Nielsen’s total outlets database, which includes national retailers such as Wal-Mart and Target, as well as some warehouse clubs and dollar store chains.

Private label dollar volume in the mass merchandisers/club/dollar store segment climbed +4.4% to $49.6 billion, resulting in a +0.5 point market share gain to 16.6%. A similar pattern emerged in regard to units, with private label advancing +4.2% compared to only +0.2% for the brands. As a result, private label’s market share moved up +0.6 of a point to 19.7%.

These gains are especially important because the total channel sales for mass merchandisers, clubs and dollar stores are climbing at a much greater rate than in the supermarket channel. Dollar volume sales for Nielsen’s all retail outlets combined segment, which also includes drug chains, outpaced the supermarkets-only measure, increasing +0.8% compared to barely +0.1% growth for supermarkets.

Store brands’ market share declined in the slow-growth supermarket channel—measured at 18.4% dollar share and 22.3% unit share—as well as in Nielsen’s all outlets combined sector, but the data clearly indicate that, separate from the adverse impact of supermarket numbers dragging down the overall private label results, market shares for retailer brands in the other outlets have experienced solid gains at the expense of national brands.

Private label’s success in mass merchandisers and other non-supermarket channels is also an important factor when estimating the total size of the private label market in the U.S.

While Nielsen reports total private label sales for 2016 at $118 billion, these results do not include sales from some of the biggest and best store brands retailers in the country, such as Costco, Aldi, and Trader Joe’s. Estimates of their private label sales would add $35 billion to the total and push the total U.S. private label market to more than $150 billion.