Brazil conducts post enumeration surveys after censuses. Are these surveys used to generate the weights to account for the census under count? According to these surveys censuses between 1970 and 2000 have between 4.3 and 7.3 percent under count.
As is noted on the comparability tabs for both the HHWT and PERWT variables, these sampling weights are provided by the national statistical office in Brazil for samples from 1970 onward. Sampling weights are typically the best way to adjust sample data to represent the larger population, however, all sample data has some associated sampling error. More specific details about the construction of sampling weights can be found on the Brazil sample description pages.