Government data from March indicates food & drink sales at restaurants surpassed those at traditional grocery stores for the first time. As you might imagine, there is a number of forces at work behind the numbers.
The U.S. Commerce Dept's "Estimated monthly sales for retail and food services" report, just released April 14, figured food & beverage sales in traditional "food & beverage stores" during March were $50.089 billion, down slightly from January and February. Sales in "food services & drinking places" were $50.384 billion, and have been going up on a monthly basis for a while.
A couple of caveats: "Food & beverage stores" do not include beer, wine and liquor stores, which add about $4 billion a month in food sales, nor do they include food sold at mass marketers such as Walmart, Costco and dollar stores – those formats have been increasing their food & beverage sales.
But the Commerce data does confirm and quantify long-running trends of food purchasing away from traditional groceries to alternate formats and restaurants, with millennials playing an increasing role in those shifts.
The full table is at http://www.census.gov/retail/marts/www/marts_current.pdf.