For example, on October 1st 1949, the People's Republic of China (PRC) was proclaimed. Would hundreds of millions of people then suddenly have switched from being citizens of the Republic of China (ROC) to the PRC?
I was inspired to ask this question because Tu Youyou has been heralded as the first science Nobel Prize winner from China (presumably meaning the PRC).
But Yang Chen-Ning and Lee Tsung-Dao also won the Physics Nobel Prize in 1957. According to Wikipedia, both moved to the USA in 1946, but became US citizens only in 1962 and 1964. So what was the citizenship of these two men when they won the Nobel Prize in 1957? The PRC or the ROC or something else?