Regardless of whether or not the DDG study is accurate, it should be taken with a grain of salt since DDG has a clear incentive to get more people onto their search instead of Google.

If their study is accurate, why it needs to be suspect just because they want people to use their service? If I provided a good service and my competitor provided a bad one, and I said "this guy does bad stuff, use my stuff instead" and you knew it's true - would you still use bad service just because I'd profit from you using the good one? That makes no sense.

Who would you trust to run a report like this? The EFF? They have a dog in the hunt too. Congress? Since they believe the internet is made of tubes, I don't trust them either. I can't think of anyone with the skillz to do this type of report will not have a bias one way or the other.

Who conducts a study without a bias? Every study is conducted a null hypothesis they seek to disprove. How unfamiliar are you with academia?

You're making the assertion. Do you have evidence to dispute the DDG study? The onus is on you.

I believe (I haven't read the study in detail) that their results show that different people get different results when not logged in. They didn't actually correlate this with anything like purchase history or individual user info. Others ha e hypothesized that the differences are due to location.

In other words, the study proves that different people get different results. It doesn't prove, as they claim in some press, that this is because Google tracks you while you aren't logged in. It's misleading on DDGs part to claim such of that's the case.

(I work at Google, but have nothing to do with ads).

As a broader point, just because you have a null hypithesis does not mean the study is biased. That's completely not how academia works.

Bias as the gp used it doesn't mean statistical bias which also isn't what you mean, but more like "even if these results are technically accurate, they may be misleading", a common example would be p-hacked results. This, contrary to what you say, often involves inventing a hypothesis after the fact, such that it is easily disproven with your data.

You make a good point that the fact that there are different results doesn't mean that they are personalized. It could simply be that Google is providing different search results so they can get better data on what people want to click. This would be a benign — indeed legitimate — explanation for the DDG study results.

However, there isn't evidence that this was what was happening, and Google hasn't exactly covered itself in glory on the privacy front so I tend not to give them the benefit of the doubt on this front. I'd love to see a response from them addressing some of the points from the DDG study.

Of course, I agree, which is why I included my own experience as a third example, or the 333rd example, or whatever it is by now. At some point all the tests with different flaws, all the personal experiences that may have other explanations, all the Google statements, the discoveries by companies and governments with vested interests...are all finding the same thing. It adds up to Google tracking us in all sorts of ways, many of which we aren't aware of, in order to give themselves the power to do things on an enormous scale, many of which we aren't aware of.

I work for Google, but not on browsing or anything related and have no special knowledge of the space or how Google handles these things.

I don't believe that Google tracks you in incognito mode. My understanding that the DDG study showed that they continue to track you when not logged in, which is consistent with Google's public statements on the matter.

regarding the duckduckgo study there is a bit more to say.

Their methodology was pretty flawed and to top it all they also results "positive" to this kind of analysis.

This does not implies that google does not track incognito users either.