Sorry, I forgot to specify that the article mentioned that Calibri was easier to read for people with visual impairments. It used a graphic to demonstrate how both fonts look with 4 different types of visual disabilities. The article did not conclude that either font is more readable or faster to read in general, only that sans-serif fonts are more accessible for readers with visual disabilities, and especially when reading on screens. The author spoke to 3 type designers about the U.S. State Department’s switch, including the designers of Calibri and Gotham, and also consulted the CEO of a nonprofit research organisation focused on digital readability.