Source Value


The following is a working document intended to describe the relative merits and demerits of various types of sources commonly employed by genealogists

CategorySource TypeAdvantageDisadvantage
Primary Source or
Original Source
Governmental, Church, and Organization, and personal records contemporary with the eventHighly accurateEven contemporary records by the participants sometimes err.
Recollections of persons who witnessed events Often highly accurate accounts Sometimes subject to information loss or corruption because considerable time may have elapsed between the event and when the eyewitness described it.
Secondary Source or Derivative SourceCorporate Entity WebSiteContain a wealth of information, usually sourced, Usually verifiable, usually not validatedOften contains a mix of verifiable and unverifiable information, sometimes contains unsourced information (e.g., Ancestry Family Trees)
Recollections of persons who knew persons contemporary with the eventsOften contain accurate information obtained first hand from eyewitnessesOften contains misunderstandings. Potential for information loss is moderate.
Published histories, biographies.Often contains well distilled information based on primary sourcesSometimes contains unsubstantiated opinion.
Mixed*Published Family GenealogiesFocused on specific lineages; typically contains a mixture of sourced and unsourced materials, sometimes contains transcripts, extracts, or abstracts of original source material; Contains conclusions based on interpretation of information developed from a mixture of primary, secondary sources that may offer considerable insight into the family historyThe authors conclusions are usually interpretative, and subject to interpretational error. Where primary and secondary sources are not cited, what they say is not verifiable, and the are best treated as tertiary sources.
Tertiary SourceGEDCOMCan be used to rapidly increase size of family tree, or to add information to individual cards in that treeUsually unsourced, unverifiable, unvalidated; a well documented GedCom, relying on at least secondary sources to document conclusions reached, can rise to the level of a secondary source. However, as an Ephemeral Source a GedComcan not be relied on in the same way as secondary sources.
Private WebSiteOften contain a distilled dicussion of family relationships and historyOften unsourced, unverifiable, unvalidated, and ephemeral. Can rise to the level of a secondary source, but as an Ephemeral Source can not be relied on in the same way as secondary sources.
Emails and Letters by GenealogistsOften contain distilled summaries of information providing useful clues to the researcherEveryone makes mistakes. Such items may not be available for other researchers to examine.

*Formally published Family Genealogies range from exceeding well done works, to works that might best be described as "well meaning". The former can be considered "secondary sources", while the latter are "tertiary sources". The distinction between the two is based on the extent to which the work in question utilizes primary and secondary sources, and documents the sources used for specific facts presented. If it relies on primary sources, then it's a secondary source; if it failes to document, or utilizes tertiary sources, then its a tertiary source.