Genealogists frequently make use of the abundant transcriptions of various documents as they seek information about their ancestors. Transcriptions of census lists, rosters, cemetery records, tax lists, and the like, provide useful information, all of which is grist for the genealogical mills. These transcriptions are commonly available on the web, and may either draw on the original documents themselves, or, more commonly, on transcriptions based on the work of previously published authors.
In working on genealogies for families in Dauphin County, Pennsylvania I've found transcriptions of tax assessment records are available for many counties and townships in the pre-revolutionary period. The work of William Egle (Egle's Notes qnd Queries) and that of I. Rupp ( are commonly cited as the source for transcriptions for these tax assessments currently presented on the web.
Recently I came to examine transcriptions of the 1751 tax assessment for East Derry Township in Dauphin County, and was surprized to find that there are no less than three separate transcriptions available on the web. One is from I Rupp's History and Topography of Dauphine County, published about XYXY and available on Google Books. Another is found in Egle's Notes and Queries published around 1900, and republished in 1970 by the Genealogical Publishing Company. This work is also available on the web, though the only version I've been able to find is one through Genealogy.com subscription service. Yet a third version is a transcription by Nancy Piper on GenealogyTrails.com. I presume both Egle and Rupp made use of the original tax records; Piper, however, transcribed the list provided by Egle in his Notes and Queries.
The existence of these three transcriptions of the same material creates an interesting opportunity to compare the accuracies of transcriptions in general. Theoretically, each of these transcriptions is based, directly or indirectly, on the original 18th century records. As such, you'd expect them to match. Unfortunately, they differ from each other substantially.
The following table summarizes tax lists for East Derry Township, Cumberland County PA, for the year 1751, as they separately appear in the work of Egle, Rupp, and Piper
From the data presented below it is clear that Egle and Rupp different in various respect in their transcriptions of the original tax assessment for East Derry in 1751.
Omissions The most serious differences are those of omission. Between the two authors, 103 individuals are identified in their transcriptions. Of these 103 persons, 25 appear only in one list or the other. Egle omits 8 names found in Rupp, while Rupp omits 17 names found in Egle. it seems likely that each author simply overlooked some of the names on the original transcription.  Given the high percentage of differences between the two lists (25% of the combined names are missing on one list or the other), it seems likely tat there were additional names overlooked by both authors.
There are other discrepancies between the two lists that can be pointed to.
Modernized Spelling Rupp appears to have modernized, standardized spellings of given names and surnames, while Egle appears to have retained the original spellings of the transcription. As an example, Rupp identifies a "John Campbell", while Egle identifies what appears to be the same person as "John Cample". Most likely the name really is the modern "John Campbell", but it may have been better to stick to the spelling as written.
Handwriting Interpretation Interpreting the handwriting in old and faded records is sometimes difficult, and one does the best one can. Odd spellings sometimes result when the transcriber has a particularly difficult time in making out the original. An example of this is Egle identifies a "John Pinogel" whereas Rupp gives him as "John Rinagel". There's no way to tell which version is right without looking at the original and seeing what the best match would be.
Name Order Tax lists are sometimes given in alphabetical format, sometimes in an "as encountered" format. The former format is useful for finding a specific individual, but the latter sometimes gives clues as to who lived near whom. In some cases the original list was alphabeticzed by the tax collector, and that's all that has been preserved. Sometimes the tax collector makes no such effort and the list preserves names in the order encountered. Sometimes a transcriber will choose to reorder the list in alphabetical order, to improve ease of use, but thereby loosing what may be useful information.
In the case of the three transcriptions dealt with here, two (Piper and Ruppe) appear to retain the original "as encountered" format.  The 1970 Genealogy Publishing version of Egle's list utilizes a semi-alphabetical ordering. The Piper Transcription and the Genealogical Publishing transcription of 1970 are both transcriptions of Egle's original work, but differ from each other in numerous details, not the least of which is "alphabetical" versus "as encountered data" order. This suggests the the two transcriptions, though ostensibly based on the same work, made use of different versions of Egle's Notes and Queries, and that perhaps one version was modified by a later hand. Possibly those modifcations represent changes made by Egle himself between different publications of his work.