A 1999 study of 50 years of second-language education at the United States Department of State's Foreign Service Institute found that adult native speakers of English required 24 weeks or 600 classroom hours to achieve general proficiency ("3" on the DLPT, or "Superior" rating on the ACTFL scale) in "Category I" closely cognate languages, such as French, Spanish, and Swedish. "Category II" languages such as Finnish, Russian, and Vietnamese required 44 weeks or 1,100 hours. The "Category III" languages Arabic, Chinese, Japanese, and Korean required 88 weeks with the second year in the language's country, or 2,200 hours.[22]