Sales at Popeyes restaurants were up 42% to $1.3 billion in the fourth calendar quarter of 2019, says Restaurant Brands International, the parent company of the chain. That’s due almost entirely to the seemingly endless popularity of the chain’s chicken sandwich.

The quarterly results are really the first chance investors have had to get a true idea of the sandwich’s impact. The initial burst of popularity, when the chain sold out of the sandwich in under two weeks, didn’t give a good picture as to the impact the sandwich would have on the bottom line. The reintroduction in November, though, has been more than a short term event.

The sandwich “has proven to be a game changer for the brand in every way,” said Restaurant Brands International (QSR) CEO Jose Cil in a statement.

For the year, Popeyes saw sales growth of 18.5%.

Sales were also on the rise at corporate cousin Burger King, which is also owned by RBI. Buoyed by the Impossible Whopper, sales jumped 8.4% at the burger chain in the fourth quarter and 9.3% for the year.

The success of Popeyes in its fight with Chick Fil A has emboldened other restaurant chains to focus on chicken sandwiches. McDonald’s is currently testing two versions of a chicken sandwich in several states. The Crispy Chicken Sandwich, it says, is topped with butter and crinkle cut dill pickles while the Deluxe Chicken Sandwich is topped with tomatoes, lettuce, and mayo. Both are served on a buttered potato roll.

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