Tuesday, May 24, 2016

More Family Finder Matches?



FTDNA project administrators should be getting notices soon that announce the following changes in the threshold Family Finder customers must meet in order to be matched with each other. For those of you who like to monitor how such changes impact the number of matches you are shown, you better document your baseline data quickly. Your number of matches should change soon. 

You asked for it - we listened!

For several years the genetic genealogy community has asked for adjustments to the matching thresholds in the Family Finder autosomal test. After months of research and testing, we have implemented some exciting changes effective very soon.
Currently, the current matching thresholds - the minimum amount of shared DNA required for two people to show as a match are:

●       Minimum longest block of at least 7.69 cM for 99% of testers, 5.5 cM for the other one percent
●       Minimum 20 total shared centiMorgans 

Some people believed those thresholds to be too restrictive, and through the years requested changes that would loosen those restrictions.

Soon, the following changes will have been implemented to the matching program.

●       No minimum shared centiMorgans, but if the cM total is less than 20, at least one segment must be 9 cM or longer.
●       If the longest block of shared DNA is greater than 9 cM, the match will show regardless of total shared cM or the number of matching segments.
The entire existing database has been rerun using the new matching criteria, and all new matches have been calculated with the new thresholds. 
Most people will see only minor changes in their matches, mostly in the speculative range. They may lose some matches but gain others.  

I am assuming that most of you will get additional matches -- particularly those formed by single shared segments between 9 and 19 cMs. This will not be close relatives but potentially could be with family members in the 4th to 6th cousin range. Such matches have been suppressed because the shared cMs totaled less than 20. They can be detected in comparisons run at GEDmatch on FTDNA data.

 Some die hard genetic genealogists love to analyze the changes in matches reported when adjustments are made such as the one that is imminent from FTDNA. Yesterday Jason Lee reported in a ISOGG Facebook post: "Two thirds of my matches at AncestryDNA are single segment matches under 9 cM." Those wishing to dissect the differences between databases and differences in a single database before and after screening criteria is changed will have a field day as FTDNA rolls out the above change.


If you want to be able to compare your "before" matches with the "after" ones, you better move fast. This change may start rolling out very soon.


Posted by Dr D at 4:06 AM
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5 comments:

  1. Jackie's BlogMay 24, 2016 at 6:34 AM

    Looking forward to the changes. Hopefully, a change for the better.

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  2. crsouserMay 24, 2016 at 10:34 AM

    I couldn't find this under their press releases, Facebook page, or under Project Administrator announcements. It apparently being sent out in waves to administrators via email vs. at once or posted to the project admin pages which is frustrating. I did call them though and they confirmed the information above is occurring but no date has been set for it to actually kick in.

    ReplyDelete
    Replies
    1. Dr DMay 24, 2016 at 10:58 AM

      The original schedule was for project administrators to get an email sometime today and for the conversion to be made late today. However, yesterday this schedule was revised to allow for a final quality control check. The database revision will be coming very soon but no specific time has been announced yet.

      Delete
  3. Dr DMay 25, 2016 at 5:42 PM

    Today FTDNA sent a message to project coordinators which contained the following information:

    "After months of research and testing, we’re implementing those changes as soon as the quality assurance process is complete, which should be within the next few days."

    "Until now the amount of shared DNA required for two people to show as a match was a minimum of 20 total centiMorgans of shared DNA with a minimum longest block of at least 7.69 cM for 99% of testers, 5.5 cM for the other one percent."

    "With the adjustment, if two people share a segment of 9 cM or more, they will show as a match regardless of the number of total shared cM. However, if there’s not a block that’s 9 cM or greater, the minimum of 20 shared cM with a longest block of 7.69 cM applies."

    "We also slightly altered other proprietary portions of the matching algorithm that will, to a small degree, affect block sizes and total shared centiMorgans. These changes should have only marginal effects, if any, on relationships, generally in the distant to remote ranges."

    "There’s a separate proprietary formula that is also applied to those with Ashkenazi heritage, but you can, of course, expect to have more new matches than those not of Ashkenazi heritage."

    "The entire existing database has been rerun using the new matching criteria, and all new matches have been calculated with the new thresholds."

    "Please keep in mind this change will not affect close matches, only distant and speculative ones. Some matches will fall off, others will be added. Most people will likely have a net gain of matches."

    "Your myOrigins results may change slightly with the rerun, but we have not updated or changed myOrigins yet. We’ll let you know when that happens."

    "And that’s not the only good news we have!
    Some of you may have dealt with mtDNA results that had some issues with genetic distance. The fix for the root cause of that problem was released awhile back, but we had to wait until all the hardware installations were complete and integrated before re-running those kits affected prior to that fix. We’re in the process of deploying that update now!"

    "Over the next few days, those affected will likely see differences in genetic distance of some matches as the corrections are implemented. Those who have tested after the fix whose mutations were correct may see an increase in matches to existing testers."

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  4. Dr DMay 26, 2016 at 7:30 AM

    The change seems to have been implemented. Of few Family Finder matches I have checked, the percentage of new matches seems to range from about 4.5% to 6.5%. So it would appear that the rich get richer. Guess that makes sense.

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