Google Analytics calculated one thing, another in the logs, the statistics of the advertising system say something else. Where is the truth?

Question

contextual advertising

Misters, I ask to prompt, in what there can be a hitch.
There is an advertising system that brings people to the site (well, wow!). There is a noticeable discrepancy between the data obtained through different statistical systems. Relatively speaking, for yesterday there were:
a) According to Google Analytics, 1000 visits,
b) According to the logs of unique ip with the required utm_cource, there were 1,159,
c) According to the statistics of the advertising system, there were 1,200 clicks.
There are no filters in GA that could exclude any transitions. About 1,000 clicks is a very significant share of visits to the site, so you can’t just write it off as an approximation error.
It's hard for me to explain why the logs show 15% more clicks. If it were the other way around, it would be understandable.
What can you suggest?

Answer 1

In my opinion, there is a possibility that Google Analytics:
1. Does not take into account those who have disabled JS or blocked their service or had JS errors (I'm not sure about the latter)
2. Based on some of its data, it recognizes those who changed their IP ( although it should take into account those who are on the same IP)
3. Takes into account the minimum visit time (if it was immediately closed, then it seems that the visit is not taken into account - I hope, if anything - they will correct me).
4. Excludes bots (due to point 1)
5. Similar to points 1 and 3 - the script did not have time to load.

Answer 2

Under Lisa (and other browsers) there was an extension, Ghostery , it perfectly blocks attempts by both Analytix and Metrica to count visits.

Answer 3

In addition to the first answer: it is possible that advertising statistics count clicks.
It happens that the user clicks on the link, but the redirect to the desired domain does not occur instantly, and the user presses F5.

Answer 4

There can be many reasons for discrepancies. Starting from the methods of determining a unique visitor/visit and ending with the location of the counter on the page (top/bottom) or the heaviness of the tracker script... Do not compare this with each other - just use the tool that is more convenient for solving a specific problem.
Even installing two counters - the old GA and the new UA - on one site you will not get the same numbers. And this is not bad. It just is. You just need to understand that Google Analytics is not an accounting system, but a tool for trend analysis. Just don't expect it to take into account "to the last penny", but use it for its intended purpose - its analytical capabilities are quite worthy.

Answer 5

Comrades, why is the opposite situation so obvious? when there are fewer clicks than conversions? I mean, if UTM is registered, then the user will not go through it the second time. Are there any other reasons?
Faced a similar situation, while the number of unique users tends to 95%.