Diners' review posted online for restaurants can be affected by more than just the food and service a study has found; weather outside can influence whether it's positive or negative.
Researchers from Yahoo Labs and Georgia Tech says they got the result by analyzing 1.1 million reviews posted online, covering 840,000 dining establishments in 32,000 U.S. cities.
Reviews posted on days when it was raining or snowing, or on days when it was either very cold or very hot, tend to be more negative than those posted on a day with nice weather, they say.
"People love to describe themselves as foodies," Georgia Tech doctoral candidate Saeideh Bakhshi, the study leader, says. "But in the end, it looks like we're all weather people, whether we realize it or not."
"The best reviews are written on sunny days between 70 and 100 degrees," Bakhshi says. "Science has shown that weather impacts our mood, so a nice day can lead to a nice review. A rainy day can mean a miserable one."
Ten years of online reviews on sites such as Citysearch, TripAdvisor and Foursquare also revealed demographic differences including education levels, neighborhood diversity and population density significantly impact the character of reviews, the researchers say.
In densely populated cities, people tend to be more accepting of longer wait times, they noted, while in smaller cities online reviews were more likely to mention slow service as a negative.
"We also found that restaurants in the Northeast and Pacific get more reviews than places in the South and Midwest," Bakhshi added. "I think the difference between the South and Pacific comes mostly from the differences in education, diversity and liberal versus conservative. Blue states such as California, Washington and Oregon have a higher number of reviews per restaurant."
Eric Gilbert of Georgia Tech's School of Interactive Computing was part of the research team along with Partha Kanuparthy, a research scientist at Yahoo Labs who graduated from Georgia Tech in 2012 with a degree in computer science.
The findings could give consumer a better understanding of online reviews, Gilbert says, while improving the caliber of recommendations provided by review sites.
"Outside factors apparently introduce bias in online ratings of a highly reviewed restaurant in big cities compared to a similar place in a rural area," Gilbert says.
Restaurants face the same challenges anyone can encounter when dealing with the "outside factor," Kanuparthy says.
"You can plan the best wedding or birthday party. Restaurants can serve great food and provide spectacular service," Gilbert added. "But no one can control the weather. In the end, you can't beat Mother Nature."
