As I read your comment, I think that some things I have said were not precise enough or oversimplified, whilst other things are misunderstood and we aren't actually disagreeing too much.

I had a long reply written out, but my computer crashed so I'll condense it. It was honestly not my intention to misrepresent the issue. As a secular Jew, I get very irritated when my non-theistic identity is disregarded, as the religious component is the most emphasised in the West. I apologise if my enthusiasm was rude, or if I made some imprecise statements.

1) I am not a geneticist. I'm just a layman. However, it seems to me that the scholarly consensus - from wikipedia articles, google search, etc. is that Jews are of a mixed ME and local origin, coming from a central population that - at least for the largest groups, sephardi and ashkenazi, split around the end of the first millenium. Haplotype commonality between these two peoples that is not present in either of their host populations suggests they originate from a single loosely defined people, made from the groups that had converted before/around 0AD. This statement could be wrong, but even if it is, I believe the evidence exists that each ethnicity itself - ashkenazic and sephardic - is genetically distinct from the native European/Arab peoples respectively. You may or may not believe me on that, and I do not have

When I speak of low conversion rates, I am speaking of after this split, so for the last 1000 years. Not mentioning this subtlety was just a simplification, since it doesn't in my view directly bear on whether modern jews form an ethnic group or not. I wasn't intending to be disingenuous by not mentioning it.

I also did not mean that Jews are solely an ethnic group, and I'm sorry that I emphasised this so much. It was a response to the dominant view of the audience that Jews are only a religion. There are those who are ethnically Jewish, but do not follow the religion, and those who are religiously Jewish, but are not of Jewish heritage. So of course, you are right that ethnic group is itself not accurate.

However, my argument is that since the conversion rate was so low, but the number of non-religious/atheist/converted Jews is so much larger than the number of people converted to Judaism, the set of people who are "ethnically" Jewish is much closer to covering the total set of Jews than merely the set of people who practice Judaism. The majority of Jews are ashkenazi or sephardi, so assuming the validity of the data, they come under common ethnicity. However, even in Israel, the percentage of secular Jews is 42% - a finding completely at odds with a religious definition. In this sense, I argue that ethnicity is a better definition than religion. However, I cannot deny that ethnoreligous group is technically the correct definition, and I only meant to argue it is an ethnic group for simplicity and as a counterpoint to the current idea.

Even if Ashkenazi and sephardi groups do not share good relation, at least one can argue that the groups are ethnically distinct within the host population. Here is a link with data I find quite convincing, but perhaps you won't.

http://scienceblogs.com/gnxp/2009/01/22/how-ashkenazi-jewish-are-you/

In short, I'm not trying to argue that they are solely an ethnicity, and I apologise for giving that impression. However, I still maintain that as an ethno-religious group, the numbers within the sets of relgious+ethnic, solely religious, and solely ethnic Jewish mean that the ethnic definition is, though incomplete, far better than the religious definition for describing the modern Jewish people.

You seem quite angry with me, and perhaps that's because I was very rude in posting the same oversimplified answer many times. I'm sorry about that, but I honestly don't think I was disingenuous or very factually wrong, and I certainly didn't mean to offend. I just wanted the ethnic identity of secular Jews, of which there are very many, to be respected.

edit: here is pictorial form of genetic data: http://dienekes.blogspot.co.uk/2010/06/genome-wide-structure-of-jews-behar-et.html

Not that it's too relevant to the argument, but it is interesting nonetheless, and since you actually look into data, you might find it interesting - in fact, do let me know what you think, since I have only given these a cursory glance.