Check out Yelp’s listing for New Woey Loy Goey in San Francisco’s Chinatown, and below its rating (3.5 stars), food photos and hours, you’ll encounter a text box that covers the individual customer reviews: “Customer Alert: Poor Food Safety Score!”

Yelp has been posting these alerts on approximately 5 percent of the city’s restaurants since 2015, and San Francisco is the only city in the country to have them. A new Harvard Business School working paper claims that the boxes reduce Yelpers’ “intention to visit” by 21 percent.

But people in the restaurant industry say the alerts also point out significant flaws in the city’s health inspection scoring system, hurting restaurants long after they may have cleaned up their act.

On March 1, Michael Luca and Daisy Dai — economics professors who helped Yelp design the alert boxes several years ago — published “Digitizing Disclosure: The Case of Restaurant Hygiene Scores,” outlining the project’s rationale and measuring its effectiveness. Luca said they were inspired by a 1998 law requiring Los Angeles restaurants to post placards on their entrances displaying their health inspection ratings, depicted as a letter grade: A, B or C.

“This became a canonical example of disclosure — how information can improve the functioning of markets and how people can make better decisions,” Luca said.

The San Francisco Department of Public Health issues health inspection scores on a 100-point scale, and restaurants may post scores in discreet locations. The public can also search the department’s site for a restaurant’s current and past ratings.

In an effort to further publicize the scores, Luca and Dai helped Yelp link restaurant listings to scores from the health department database in 2013, and Yelp began posting them at the top of each restaurant’s page, right below the hours of operation. According to Luca, posting scores “allows you to reach customers when they’re making a decision,” rather than at a later moment when they arrive at the restaurant. Two years later, the economists worked with Yelp to create an alert for restaurants with scores of 70 or below, which the department classifies as “poor.”

Not surprisingly, the Golden Gate Restaurant Association is not thrilled with the Yelp program. The health department scores are entirely based on routine inspections, conducted between every six and 18 months. But the posted scores may not always reflect the current cleanliness of the venue, association head Gwyneth Borden said.

“If you get a bad inspection from the Department of Public Health, anything below 70, (the inspectors) come back in a week. You must have corrected high-risk violations or you would be shut down,” said Borden. “If you see that 70, that was fixed within a week. You fix the violations, but live with the score until the next inspection.”

More disturbingly, Borden points out, if customers complain to the health department about a violation and the inspectors respond by paying a visit — even shutting the restaurant down — that non-routine inspection doesn’t result in a score.

“If the restaurant is open, that means they’ve been inspected and should be safe to eat,” said Rachel Kagan, spokeswoman for the health department. “We are not out to punish restaurants. We work with them all the time to improve food handling practices and safety.”

Tracking the effects of scores — and the Yelp alerts — is impossible without obtaining detailed sales data from restaurants, Luca and Dai admit. Both Kagan and Borden said they have heard anecdotal reports from restaurateurs that low scores have indeed affected sales.

The economists used a number of online metrics to come to their conclusion, Dai said: “The measures we use, when people land on this page, do they click on the restaurant’s URL link or on the telephone number to call? Do they search for directions? Do they tend to write a review afterward?”

According to these measures, which did track individual users at a “granular” level — yes, Yelp can record your searches and what you do with the findings — customers were 12 percent less likely to pursue such actions on listings with low scores, and an additional 9 percent less likely to do so when an alert box appears. Furthermore, visitors who have encountered an alert are 10 percent less likely to leave a review.

Yelp’s alert-box practices, and the study methodology, do raise concerns.

Why doesn’t an alert box appear with Cafe Prague (score: 68) or Lam Hoa Thuan (score: 60), but does with New Woey Loy Goey (score: 70)?

Does a failure to click on a map mean that a diner will actually avoid a restaurant? Are regulars of a restaurant even likely to check Yelp scores?

Borden suggests that shortening the time between inspections would keep restaurants from growing lax with hygiene. “The challenge in assessing health risks has less to do with a snapshot and more when there are long periods between inspections,” she said.

Luca said that, for him, the purpose of using Yelp alerts isn’t just to steer diners away from restaurants with significant violations. He considers public scores an accountability system. “They cause restaurants to clean up,” he said. “They’re a high-powered incentive for restaurants not to do poorly in the first case.”