Excerpt from change request document:

A sociolinguistic survey of the Suba peoples of Tarime District, Mara Region, Tanzania, was carried out by the SIL Tanzania Language Assessment Team in January and February 2006. This survey also included a short stay on Mfangano Island in Kenya, which is the heartland of the Kenyan Suba people and their language. During this time a 300-word wordlist was elicited in the Kenyan variety of Suba, and a 3-minute story was digitally recorded. The team then returned to Tanzania and spent 2 weeks researching the Tanzanian varieties spoken by the Suba and Simbiti peoples. In a total of 6 research locations wordlists were elicited and groups of people were invited to listen to the story elicited in Kenyan Suba. Almost without exception the Tanzanian Suba and Simbiti peoples had a great deal of difficulty understanding the Kenyan Suba, and all reported that it was more difficult to understand than the nearby Kuria and Zanaki languages. The comparison of wordlists similarly showed that the Kenyan Suba variety and the Tanzanian Suba and Simbiti varieties are distinct languages.

Therefore the Language Assessment Team concluded that the Suba and Simbiti varieties hitherto considered to be part of the same language as that spoken by the Suba in Kenya, do in fact constitute a distinct language.