Another aspect of census records that often leads to erroneous information is family relationships. It was the census of 1850 that began listing the names of each individual in the household. But, it wasn't until 1880 that the census included listing the relationship of each person to the head of household. Since most of the 1890 census was destroyed, in reality most of us don't have access to that information until census year 1900.
The most common mistake, by beginners and even long-time family researchers, is to assume that the younger people listed on the census are children of the head of household. Look at the following actual census transcription from 1850 Alabama.
May J H 51 M planter 21,500 SC
May Mary 38 F SC
May Jack 24 M farmer Ala
May Pickens 21 M farmer Ala
May Moody 19 M Ala
May James 10 M Ala
May Benjamin 7 M Ala
One assumes that Mary is the wife of J.H. That is one possibility. It is also possible that J.H. was the childless brother of widowed Mary's deceased husband. He stepped in the help run the farm. If we go with the scenario that Mary is the spouse of J.H., are the children her's? There is a 13 year difference in ages between J.H. and Mary. She could be a second wife or third wife.
On the other hand, Mary could have married at age 14 and be the mother of all the children. Are all the younger people children of J.H.? Perhaps. Then again, perhaps both J.H. and Mary lost their spouses. We could be looking at a combined family with the two youngest being children of Mary's prior marriage. It is also possible that the two youngest children are just visiting that day. They may be nephews of J.H. Jack or Pickens or both of them could be the younger brothers of J.H., not his children at all.
Another assumption often made is that a person with a particular given name is the same person from one census to the next. Even if you found Mary in the prior census, it does not mean the Mary of 1850 is the Mary of 1840. Men often married women with the same given name; and when widowed, they often married a sister of their deceased wife. Watch for other documentation, marriage and death records as well as additional census year records to help build your preponderance of evidence.
I mentioned at the beginning of this article that it wasn't until 1880 that the census included listing the relationship of each person to the head of household. In that regard I need to again point out a word of caution. We do not know who gave the census taker the information. If it was a neighbor, they may have made presumptions on relationships, just as I am asking you not to do.
It can get a little nerve wracking playing what-if with older census records. However, it brings out the point that assumptions on census records can get you into trouble.