Hi,
In Brazil’s 2000 Census, I downloaded worker data by industry. The industry codes have five-digits and two-digits. What is the industry classification standard based on?
As noted on the INDGEN description tab, the two-digit classification is intended to broadly conform to the International Standard Industrial Classification (ISIC); my colleague who works on IPUMS International and is familiar with these variables suggested that this is likely closer to ISIC revision 3 or 3.1. The IND description tab notes that the detailed industry code is whatever was used by the respective national census office at the time of data collection; neither my colleague nor I was able to find information about which specific classification is being used. However, the Brazilian Institute of Geography and Statistics (IGBE) webpage seems to be down, which is where I would hope to find more information. At this point, the best advice I can offer is to check https://www.ibge.gov.br once it is back online. You may want to search for " Classificação Nacional de Atividades Econômicas". I am sure you were hoping for more definitive information, but hope this helps.
It looks like the IGBE site is back up. Based on notes in the drop-down option from this search page I would look into the first and second edition of the 1.0 version of the classification for more details.