It takes four years of knowing someone before they can be considered a ‘best’ friend, according to new research. A poll of 2,000 Americans found the average respondent needs to go through four different personal experiences with a friend before they can qualify them as a best friend.

The study, conducted by OnePoll on behalf of Evite, aimed to reveal what friendship means to Americans — and uncovered two in five must go through a life-changing experience with a friend before they can upgrade them to a ‘best’ friend.

One in three said they must go on a vacation with a friend before earning the moniker of best friend, while a further one in five has to share clothes first. The results showed that Americans would do almost anything for their besties, including traveling across the country (42%) and keeping their secrets (36%).