In the 2000 Brazilian census, I have not a single observation in the state of Acre for which the variable indgen indicates “mining” (indgen=20).
In comparison, still for Acre and the mining sector, I have:
-2 observations in 1980
-14 observations in 1991
-4 observations in 2010
Admittedly, the mining sector is very very small in this state whatever the year considered. However, I don’t believe it be completely inexistent in year 2000. In consequence, is there something wrong with my data extract?
Notice that the issue is not related to the percentage of data extracted in each year since it is for instance larger in 2000 (4%) than in 2010 (2%).