Sentence:  Too much should not be made of it, in view of statistical uncertainties above detailed, but the largest shift in the whole of Table III is in the case of Russia. Only 26.1 per cent of natives of Russia were naturalized in 1910, but in 1920 the percentage was 15.6 higher. It would be interesting to know how much was pre-Soviet and how much <WSD>post-Soviet</WSD>, and a tabulation by year of arrival and year of naturalization would disclose it. 
Meaning of the word marked with <WSD> tags:  After the formation of the Soviet Union.