Census records are one of most basic resources used by genealogists. These records include a wealth of information that is obviously useful to researchers, as well as hidden clues that are less obvious but equally useful. Their use must be tempered with a good dose of skepticism however, as they are by their nature full of flaws.
Census records can give us clues that open up our family histories. Many beginners get so enthusiastic with what they find in census records that they go no further -- that is a big mistake. Others take down information that looks helpful, then never give that census another thought. That can be a mistake too, as we will see - it is often useful to go back to census records as we uncover further information from other sources.
There are a wide variety of census records, from various countries and many time periods. It is an ancient form of governmental record-keeping. In Bible it was because of census that Joseph and Mary had to go to Bethlehem. One of most famous surviving census records is Domesday Book from England, which dates from 1085 A.D.
In addition to actual census records, we often have recourse to what are termed 'census substitutes' -- records that have some of characteristics of censuses, and that may be used to same end. Early census records are often what are called "head of household" censuses, since only head of each family is mentioned by name. Certain tax and property records may serve same function as a head-of-household census, if it is widespread enough to encompass a large proportion of households.
Censuses were primarily designed to allow government to assess taxes, or determine what pool of available military-age men might be. They also provided a count of citizens, and perhaps a count of eligible voters for a particular area.
Beginning in 1800's, various governments were persuaded that census could serve certain social ends, in addition to their traditional functions of property evaluation and/or military assessment. To this end, additional information began to be gathered. The birthplace of individuals could help identify migration patterns. Questions could be asked regarding literacy, fluency, race, occupation, religion, relationships, mortality and more. ALL of additional data these more modern censuses provide can be used by genealogist to better understand their ancestors.
However complete or incomplete information a particular census provides, genealogist needs to keep in mind that census records tend to be full of errors. One need only consider source of information, and how it is collected, to understand how errors are likely to creep in. Some people are suspicious of government in any guise, and purposely mislead census taker. Others simply give erroneous information because they don't know correct answers. The census taker is likely to be over-worked, and may get careless. It was not unusual for records to be taken down in field, then transcribed onto clean, official forms at some later date -- and any transcription is subject to errors. No census is complete, there are always people who get missed, either through mistake, or because they don't want to be included. It has also been known to occur that persons, or entire families are listed more than once. Remote communities sometimes expected to gain from inflating their populations! Unscrupulous census takers who were paid according to number of entries they made were also motivated to repeat -- or create fictitious -- entries.
Census records are often indexed, some of those indexes provide every name in census records, others only head of each household and others in that household with surnames that differ from head of household. These indexes are wonderful tools. Like census records themselves, they are rife with errors, but if you keep that in mind, and use them judiciously they can save you hours of searching. Since original records are usually handwritten, it is easy for mis-readings to occur. The motivations of persons doing transcription must be considered -- if they get paid regardless of how accurate transcription, some people will not make an effort to be accurate. The qualifications of transcriber can also affect quality. Volunteers are hard to find, and experienced volunteers are even more elusive. When original records are faded, or in hand of a poor writer, even best transcriber will make some mistakes.
The novice genealogist will sometimes make grand gaffe of citing a census index as if it were itself a source. An index is a finding aid, it should never be used as source of information. True, an index may indicate place of residence for an individual at time of a particular census, but always go to original census record for full details. First, there will be much more information there, and secondly, you avoid perpetuating many of mistakes inherent in index. As a rule, all indexes should be treated as finding aids, not as sources in and of themselves. The only exception is in those rare cases when original records have been destroyed, but an index remains.
This sounds like an intolerable situation doesn't it? Census indexes full of errors, based on original records that are themselves full of mistakes! But if you are aware of potential problems, there is still a wealth of information available from census records. I like to think of census record itself as a kind of index -- it provides an approximate date of birth, which allows me to find birth or baptism record more easily; it provides an approximate marriage date, so I can find marriage record more easily. If I don't find those records in time and place suggested by census, I suspect error in census, and begin looking for other clues. By same token, if I don't find someone listed in a census index where I think they should be, I may go directly to census itself, assuming there is an error in index.