I noticed that in some censuses, e.g. Senegal 1998 and 2002, ethnicities that have the same name are encoded with different numerical value. E.g. in the Censuses of Senegal “Wolof” is assigned the code 113 and 130, where 113 is only available in 2002, but 130 is available in both years. Is this an error in the coding, or are they supposed to refer to different ethnic groups. It seems there are more countries where this happens.