The text and coding of the question in the IPUMs data is a bit misleading. According to Ipums:
desc This variable indicates whether the person was born in the municipality where he/she is currently living.
|0|NIU (not in universe)|12,302,283|
This is a literal translation of the variable “4.17 - NASCEU NESTE MUNICÍPIO?”.
But if you flow the questionnaire, this question is only reached with you answer no to a previous question:
“4.15 - MORA NESTE MUNICÍPIO DESDE QUE NASCEU?”
therefore the NIU cases are all people born in the current municipality
Should I communicate these problems here or by email (I rather do it here). Do I still get a mug?