Retailers are earning a lousy reputation for not responding to tweets.

One recent study found that a mere 29 percent of retailers with Twitter accounts respond to customer questions and complaints.

An experiment by Software Advice on the Customer Service Investigator blog underscores this apparent indifference. The company conducted what it called “The Great Customer Service Race,” in which four people tweeted to 14 major brands over 26 days.

The point of all that tweeting was to gauge how long it took these brands to respond to customer questions and complaints, as well as their overall response rate.

Each company received one tweet a weekday. Tweets sent during the first and third weeks included the @ symbol. For the second and fourth weeks, the company’s name was mention in tweets without the @ symbol.

According to Ashley Verrill, managing editor of Customer Service Investigator, the questions asked in the tweets represented five categories:

• Urgent, or I need help right this second;
• Positive (“thank you!”);
• Negative;
• A question from their FAQ page;
• Technical, or needs more than one interaction to solve.

Many of the companies—including Apple, Starbucks, and Wal-Mart—didn’t respond at all. Bank of America, meanwhile, scored the highest response rate; MasterCard Pepsi clocked the fastest response time (34 19 minutes).

This infographic lays out the results: