Restaurants are perceived as some of the most straightforward and simple businesses in the world, which has major implications for sales growth, according to a new “2013 Global Brand Simplicity Index” from Siegel + Gale.

The New York-based global branding firm has found that when consumers view businesses as simple, they’ll be more likely to return or spend more money there.

“Depending on the industry, up to 29 percent of people are willing to pay more for simpler experiences and interactions; the amount they are willing to pay varies by industry but is significant,” the report said.

U.S. restaurant customers also said they would be willing to pay as much as 4 percent more for a dining-out experience if the offering were simpler. According to Siegel + Gale’s estimates, that could mean the potential for more than $3 billion in annual sales growth for the restaurant industry.

Siegel + Gale’s report also found that 75 percent of consumers are more likely to recommend a brand because it provides simpler experiences and communications.

“[Simplicity] brings clarity instead of confusion, decision instead of doubt, and the rewards are real,” the report said. “Simplicity inspires deeper trust and greater loyalty in customers and clears the way to innovation for employees.”

Siegel + Gale measured brands’ perceived simplicity by surveying more than 10,000 consumers in seven countries and asking them to rate those companies’ levels of simplicity or complexity in their products, services, interactions and communications. The resulting index scores ranged from roughly zero to 1,000, and restaurants like McDonald’s, KFC and Pizza Hut kept pace with other global brands like Amazon.com, Google and Aldi in terms of being viewed as simple.

As an industry, restaurants had the third-highest overall simplicity index score in Siegel + Gale’s global rankings, at 734 out of 1,000, placing behind Internet search companies and electronics manufacturers. The restaurants that placed among the 92 simplest brands in the study’s global rankings were McDonald’s, KFC, Pizza Hut, Burger King, Subway and Starbucks Coffee, at Nos. 4, 5, 10, 11, 15 and 17, respectively.