Thomas “Tommy” Rot and the Trouble with Transpositions

I’ve recently been searching for a family with the surname “Thomas” and discovered a quirk with Ancestry’s search filters.  Ancestry does not appear to be using a Soundex system for name searches. 
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Soundex is a code based on the first letter of the surname and the next three consonants.  Consonants are divided up into six groups of letters that sound similar to each other.  Vowels and the letters “H,” “W,” and “Y” are not considered in the Soundex system unless they fall at the beginning of a name.  So two names with the same consonants in the same order should be found on a search.
 
I was searching the 1940 census on Ancestry for Cordelia THOMAS born in Nebraska.  I could not come up with her.  I finally had to resort to a first-name only search and use some additional first names of other people I expected to see in the household.  With that grouping of names, I eventually hit upon Roy THOAMS and family.  

​When I looked at the census image for the family, the enumerator wrote THOMAS – however the indexer for Ancestry transposed the “M” and “A” and indexed it as THOAMS.

Year: 1940; Census Place: Longmont, Boulder, Colorado; Roll: T627_457; Page: 5A; Enumeration District: 7-49A

 
THOMAS and THOAMS have the same consonants in the same order.  In a true Soundex system, they would be indexed in the same group of names.  But Ancestry does not always put them together.  I have found dozens and dozens of THOMAS families indexed as THOAMS.  And in my spot check of people listed with the surname THOAMS in Ancestry, every single one I looked at on the census was a THOMAS.

A couple of takeaways –
If you know other family members in the household, try searching just by first name.  Unfortunately, I don’t always know other household members. 

Remember that Ancestry doesn’t use a straight-up Soundex.  You might have to think of alternate ways to spell even simple surname. And be sure to consider transposition errors.

if you are interested in more strategies for finding people on the census, check out my "Censational Census Strategies" talk.  You can see when I'll be giving it presentation schedule on the "Lectures" tab of my website.