The INSIDER Summary:

According to the Wall Street Journal, only one in five millennials, the country's largest demographic, has tried a McDonald's Big Mac.

The Big Mac is iconic, and has been the restaurant’s most recognizable menu item since 1968.

Its decline among younger consumers shows how McDonald's is struggling to compete with new, fast-casual burger joints.

Hamburger sales at the restaurant chain are flat across the board.

Though McDonald’s has been no stranger to controversy and criticism over the years, the Wall Street Journal dropped a serious bombshell last week when it reported that only one-in-five millennials — currently the country’s largest demographic — has ever eaten the fast-food chain’s iconic Big Mac.

Since its inception in 1968, the Big Mac — two patties separated by an extra slice of bread in the middle, then slathered in special sauce — has been the restaurant’s most recognizable menu item, and a symbol of American fast-food. Its decline among younger consumers marks a larger problem at the Golden Arches, as the company struggles to compete with a slew of new, fast-casual burger joints promising higher quality meat and ingredients.

The Big Mac “has gotten less relevant,” a top McDonald’s franchisee wrote in a memo this summer, according to the Journal. Not only have four-out-of-five millennials never tasted a Big Mac, but hamburger sales at the restaurant chain are flat across the board, former high-ranking McDonald’s executives told the paper.

“We have to nail it,” Mike Andres, the president of McDonald’s USA, said in an interview. “How do we deliver the best burger at the speed of McDonald’s and, ultimately, at the value you’d expect from McDonald’s? That’s what we’re working towards.”

To be fair, McDonald’s has been making a number of positive changes to its menu in recent months, seemingly in effort to keep up with the evolving fast-casual scene. America rejoiced when the company announced it would be introducing all-day breakfast last year , and on a more serious note McDonald’s also recently removed artificial preservatives from its chicken products, and shifted from frozen burger patties to fresh beef . All of these moves should, in theory, to appeal to younger, more health-conscious customers, but apparently the Big Mac still hasn’t been getting much love lately.

As the Journal notes, McDonald’s has attempted to introduce more gourmet-sounding burgers in recent months — like a sirloin burger with sauteed mushrooms and peppercorn sauce — but they rarely meet sales expectations.

“Every time they go outside of their space, they fail,” Larry Light, a former marketing chief for the company, told the publication, adding that McDonald’s should stick to improving their “staple” burgers like the Big Mac.

According to the Journal, McDonald’s will be introducing two new Big Macs next year: the Grand Mac, which is bigger than the current model, and the Mac Jr., the smallest of the Macs.

Still, there’s no word on whether millennials will pause long enough from their ShackBurgers and In-N-Out Double-Doubles to find out how these new items actually taste.