However, getting complete and accurate census information is much more difficult than one might realize. Viewing a government video created for the 1940 census (records which were only released last year) is illuminating. Even though the film uses a mock census interview, it shows how demanding the process was and one can imagine how many ways it could involve errors.
Problems of getting valid information about Chinese immigrants is especially difficult. The unfamiliarity of Chinese names for census enumerators (most, if not all, from white European backgrounds) made for problems of accurate transliteration of names. The name order for Chinese being the reverse of Eurocentric names added inaccuracy. Distrust and fear of the purpose of the census, especially for the many Chinese with false or paper son names, undoubtedly led them to be absent when the census taker came. An earlier post gives more details of these problems that existed with census records of Chinese.
One illustration of other problems was the egregious error in some census data involved confusion of the codes used to distinguish Chinese (C 4) from Colored (C 2), the term used for decades for black Americans leading to an "overcount" in some cases because "Colored" was counted as "Chinese"as detailed not only for 1940, but also as early as 1910. These are only two small examples of errors involving the count of Chinese. They are just the "tip of an iceberg" but I did not try to determine how large that iceberg might have been.