You'll get a number of answers, so I'm just starting the ball rolling. But I think you'll understand the problem better, by the diversity of these answers. Similarly, both the similarities and the differences in the admixture reports together produce a clearer picture of your true heritage.
I'm sure you won't like the first part of my answer, because it seems so wrong, but the fact is that while the admixture reports look so different and conflicting, to a large extent they are actually ALL correct. The problem is they all use different methodologies. And the science is still very young, constantly changing, improving as they continue gathering data. Some of the factors that make them so different:
- they classify populations differently
- they include very different populations, both as to region and as to age
- they base their determinations on differing sets of SNP's and genes
- they base their statistics on differing testing groups (often many more English speaking than non-English, especially British Isles, and many more Western civilization than Eastern)
- and there's no way for each geneticist to exclude their own bias's; they each tend to specialize on populations of specific regions and time periods
It's important also to understand what general population age each analysis is based on. For example, if populations like German, Italian, and French are mentioned, then you know the analysis and report are concentrating on very recent times, within the last 2 millennia only. If you see hunters and gatherers mentioned, then you know they are talking about much older populations, by many thousands of years. The reports from these 2 examples would be totally different, and yet both would be correct. I really really wish that all admixture reports would provide a general time period for the populations they associate with your results. Users need to know that while we came from certain countries in recent times, those people came from very different regions thousands of years before that. For example, take the Amerindian population. If you find evidence of Amerindian, then you *have* to find evidence of East Asians too, because Native Americans came from East Asia. But then you should also be able to find West Asian, because East Asians came from West Asia!
There have been so many human migrations, waves of populations flowing one way, then back again, and later repeating a similar trail, and mixing with the previous migrations.
This is why I don't believe you should ever trust the results of any one analysis. You will always get a better picture by combining multiple reports. And those exact percentages they like to show? Ridiculous! 5% is the same as 7%, and anything less than 1% is unreliable.