Uber is officially the best friend of business travelers.

A new study found that 6% of all business travel transactions in 2016 were with Uber, making the ridesharing company the most common expense, in terms of transactions. Uber grabbed the honor from Starbucks, which remains the most popular meal expense.

Certify, a provider of travel and expense software for companies, analyzed 40 million expenses from 1 million business travelers for the study.

The findings are a reminder of the rapid growth of ridesharing, and the challenging future for traditional car rental companies and taxis. Both Uber and its competitor Lyft saw huge gains in 2015, while taxi and rental cars suffered.

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The news comes a day after Lyft announced it was expanding to 40 more U.S. cities, and would open in 100 more by the year's end.

Uber and Lyft aren't the only sharing economy businesses to see gains. The number of Airbnb transactions has doubled each year since 2014, according to Certify.

While Uber is the most common expense by transaction, it's still far from where the most dollars are spent. Certify found that the most money was spent on airfare, followed by hotels.