The 1940 census includes several census codes or notations that can help researchers learn a little more about their ancestors.
The first notation to know about is the that usually appears after a person's name in the household entry. This circled-X indicates that person is the informant. That is, in the above example Anna B. Daly provided the information to the census enumerator.
This is really important information because we now know who provided the information. Before the 1940 census we had no clue who provided the information. Could it be the mother? The father? The 10 year old sitting on the pourch? A neighbor?
The other interesting code I recently came across is the > notation that might appear after a person's name. This code means that the person was absent – that is, not at home – for some reasong. The address is probably the person's official address but he or she is not living there whent he census taker is asking the questions.
In the above example, the occupation columns (below) indicate that John C. Daly was at "school in Europe". So he is technically still living at home but he's in college (he's 24 years old). Unfortunately for me, I don't know what country he was in. This becomes more interesting when you consider the census was taken on April 1, 1940. World War II was just getting underway. The phony war was still holding on the western front and Germany was about to invade Denmark and Norway.
I'm sure there are more census codes, such as the "O" or "R" in column 4 to indicate if they own or rent their home, but these are the two I ran across today. As with any census there may also be stray marks or marks the census taker made for his or her use. Many happened while counting the number of answers for a specific question.