Have you notice that Ancestry lowered the cM on shared matches?

Question

I've noticed that when you look at your shared matched with a DNA match it doesn't seem to show matches under 20 cM, it use to shoe more shared matches with cM less than 20.

Answer 1

Hi, David. Roberta Estes went into some detail about this very topic in her blog post from just over two weeks ago. You aren't the only one who did a head-tilt at what AncestryDNA is presenting. The explanation isn't exactly inuitive...at least not at first. But Roberta does a good job explaining it, and I think her article could help clarify things for everyone who's trying to figure out where the demarcation lines are.

Comments

Thanks for the best-answer star, Tommy. Roberta did all the heavy lifting on that one. 

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https://www.wikitree.com/g2g/user/Williams-49144 you would've gotten the Best Answer from me as well.  

Thanks for the post.

David Anthony Taylor

Answer 2

not obviously David.

are you sure you aren't looking at one of your own smaller matches?

No matter how small your match is to you, Ancestry will still show any shared matches who share more than 20cMs with both of you.

Comments

This is only when you're looking at all you matches, not when you're comparing them to one of your matches

Answer 3

Hi David, could you be a bit more specific?  I'm not sure what you are saying.  Thanks.

Comments

I've updated the question

Answer 4

No, could you explain the differences you're seeing?

Comments

I updated the question.

Answer 5

The lowest match I see is at 8 cM.

Comments

Tommy Buch I understand, now click on one of your matches over50 cM and you will notice when you select shared matches it will not show anyone under 20 cM

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Right. 20 cM is the floor value that Ancestry set for "Close" matches.

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Thanks  Tommy Buch

Answer 6

To be clear, it has been exactly this way on AncestryDNA for at least as long as I've been there, which is about 5 years. Nothing has been "lowered".

With that being said, it IS important to understand about this, and it seems like a lot of people don't.

Suppose I have a couple of 4th cousins who are siblings, themselves. Further suppose that I match John by 25cm, but only match his sister, Jane, by 15cM. As siblings, they will obviously match each other.

If I look at my Shared Matches list for John, Jane will NOT appear on it - even though she obviously matches both me and John - because she's BELOW the 20cM threshold.

However, if I look at my Shared Matches list for Jane, then John WILL appear, because he's ABOVE the 20cM threshold. So you can find out who SOME of the shared matches of John are, but who are left off his list because they're below 20cM, in this way.

Sometimes I will add a note to cousins like John that tell me what additional shared matches he has that are below 20cM (like Jane). Of course, such a list will always be incomplete, but it can be useful anyway.

Also, keep in mind that if cousin A and cousin B are BOTH below 20cM, you simply cannot tell whether A & B match each other or not (aside from asking them).