Where do millennials want to eat lunch?

If you are a marketing executive at McDonald’s, this is the question that keeps you up at night.

The rest of us have an interest because younger Americans, like members of all generations, make an impact on the culture at large by expressing their tastes.

If we may generalize: The millennials (late teens to early 30s) embrace technology and tattoos, helped elect Barack Obama to the presidency twice — and they don’t feel much love for McDonald’s. This has enormous implications for the world’s largest restaurant chain and for everyone’s eating habits.

You wouldn’t notice problems by visiting a few McDonald’s: The Golden Arches are just as ubiquitous as ever, and many stores have been remodeled. But sales in the United States have been flat or slipping for the past year or two, and a crucial reason is the young adults.

The Wall Street Journal, citing research from Chicago-based Technomic, says the number of people ages 19 to 21 in the United States who visit McDonald’s monthly has fallen by 12.9 percentage points since the beginning of 2011. That’s a disastrous performance with long-term repercussions for the business if it doesn’t turn around.

Customers ages 22 to 37 have kept their visits steady, but in the cutthroat fast-food business, you are either growing or you’re falling behind. Instead of McDonald’s, many millennials are seeking out chains that offer fare they believe is better-quality, fresher and healthier, and where they can customize their orders.

Customize? This is a generation that doesn’t listen passively to albums; it makes playlists of preferred songs. And it binge-watches favorite TV shows when and where it wishes. Same with eating. So it’s off to restaurants that let you order exactly what you want such as sandwiches from Subway or burritos from Chipotle Mexican Grill or hamburgers from Five Guys. Five Guys claims, by the way, that there are more than 250,000 ways to order a burger there.

We’re not here to give advice. We don’t do marketing-speak. But we’ve seen McDonald’s adapt to changing tastes before. When Starbucks burst on the scene, McDonald’s successfully reinvented its coffee menu, and now you can get a good cup for a $1, plus free Wi-Fi. Brands do rise and fall. The ones that survive and thrive understand their customers and give them reasons to keep coming back.

Your move, McDonald’s.