If you're in a hurry, Baltimore may not be the best place to do business.

Baltimore residents spend the most amount of time waiting in line to check out at the grocery store, see a bank teller, purchase clothes, or get a quick meal, according to a new customer-service survey.

The survey, conducted by the Mystery Shopping Providers Association, measured the average amount of time customers wait in line at banks, fast-food restaurants, department stores, and other retail establishments. The Dallas-based association hires "mystery shoppers " to go undercover and evaluate their customer experience.

With an average wait time of 5 minutes, 13 seconds, Baltimore ranked last in the comparison of customer service speed in the 25 most-populous U.S. cities. Phoenix  had the shortest average wait for service at 3 minutes, 5 seconds. Residents of Portland, Ore., finished second, with an average wait time of 3 minutes, 30 seconds, and Minneapolis came in at third place, with 3 minutes, 41 seconds.

"This study is invaluable to business owners who want to understand how their companies are stacking up against industry and city averages," John Swinburn, Mystery Shopping's executive director, said in a statement.

Gas station convenience stores offered the shortest wait time of any category of establishments studied, with a nationwide average of 2 minutes, 17 seconds. Fast-food restaurants (3 minutes, 16 seconds) and sit-down restaurants (3 minutes, 28 seconds) also had relatively short waits. Retail establishments required customers to wait in line the longest, with department-store wait times averaging 5 minutes, 23 seconds.

Survey participants were also asked if the amount of time they waited in line would affect their desire to return to the same location. In Baltimore, 77.3 percent of shoppers would return to the same location despite the wait time. Cities with the longest wait times had similar return statistics. In Washington, D.C., for example, 77 percent of customers would return to the same establishment; in Cleveland 77.7 percent; in Orlando 78.1 percent; and in Detroit 79.6 percent.