In-N-Out burger and fries. Flickr/Laine Trees Fast-food shoppers are more loyal to In-N-Out than any other chain in the business.

In-N-Out customers are more likely to recommend the chain to friends than customers of any other fast-food chain, according to new brand advocacy rankings from YouGov BrandIndex. The West Coast burger chain earned the top score of 52.4, from a range of -100 (would never recommend) to 100 (would always recommend).

According to YouGov BrandIndex CEO Ted Marzilli, In-N-Out's scarcity is key to customers' intense loyalty.

Marzilli told Business Insider that, while YouGov didn't measure exactly why some chains garner more loyalty than others, people may be more likely to recommend In-N-Out because it presents a chance to brag that they've had the chance to visit — an opportunity you would only get if you're on the West Coast.

"In-N-Out is a bit of a scarce resource," said Marzilli. "Burgers and fries don't travel very well."

Critics have said that the 313-location chain's regional nature leads to the "over-hyping" of In-N-Out, with customers singing its praises simply because it is so exclusive.

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"This regional scarcity has played with the minds of burger fans and West Coast residents, realizing they can't get their precious burgers when they travel to other areas," wrote Business Insider's Dennis Green. "Californians should be embarrassed that they fell for this psychological trick hook, line, and sinker and have even gone as far as to integrate it into the regional identity."

Food writer Andy Kryza is another In-N-Out skeptic.

"In-N-Out is beloved by your friends, who encourage you to go for a quickie whenever you can," Kryza wrote in Thrillist. "On my first taste, excitement slowly turned into crippling disappointment. It couldn't be that this legendary burger wasn't great. It must have been a fluke... But it's not. The only constant is the constant disappointment."

Still, Marzilli says that chains can't rely on exclusivity alone. Food quality and dining experience are also key — and have helped provide further reasons for In-N-Out to stay on the West Coast.

"You can argue it's harder to maintain control [over food quality and restaurant management] as you get bigger," said Marzilli.

In-N-Out says it will not expand because it wants to continue to serve food that is fresh and never frozen. That means all locations need to be relatively near distribution centers in Baldwin Park, California, and Dallas.