Zhejiang:

Throughout history there have been a series of lingua francas in the area to allow for better communication. The dialects spoken in Hangzhou, Shaoxing, and Ningbo have taken on this role historically. Since the founding of the People's Republic of China in 1949, Mandarin, which is not mutually intelligible with any of the local dialects, has been promoted as the standard language of communication throughout China. As a result, most of the population now can, to some degree, speak and comprehend Mandarin and can code-switch when necessary. A majority of the population educated since 1978 can speak Mandarin. Urban residents tend to be more fluent in Mandarin than rural people. Nevertheless, a Zhejiang accent is detectable in almost everyone from the area communicating in Mandarin, and the home dialect remains an important part of the everyday lives and cultural identities of most Zhejiang residents.

Please answer a question about this article. If the question is unanswerable, say "unanswerable". What has been not promoted as the standard language of communication throughout China since 1949?
unanswerable