Why are the new users are different depending on the period?

I've recently begun using GA4 and have a query. I attempted to determine the number of new Korean users who triggered a specific web event within a defined time frame. When I set the period from June 1st to July 23rd, it shows zero users for specific dates (July 12th to July 14th). However, when I change the period to July 12th to July 23rd, the data is no longer zero for any date.

I'm curious about the reason for this data discrepancy based on the selected time frame.

Thank you.

Hi,

The reason here is data sampling by GA4. This happens when -

1. the hits in GA4 exceed 10 million events. Also, when you add dimensions like gender, age, and interest as primary or secondary dimensions, segments, or comparisons to your GA4 report, then the hit limits apply.
2. data sampling occurs in GA4 reporting if your data is limited or your website attracts scarce traffic.
3. if your reports contain several high-cardinality dimensions (over 25,000 unique values), then GA4 will apply data sampling to your reports.

You can troubleshoot this too - Everything You Need to Know About Data Sampling in GA4

Appreciate your response, @agkhy .

Just one more question -

You mentioned that in GA4, data sampling occurs when the hits surpass 10 million events. Does this 10 million events refer to the total events logged in GA4, or is it specific to a single event? I believe the overall events generated by our service exceed 10 million, but the particular event I mentioned does not.

10 million events for all the events logged into GA4. Not just one event. If the sum total of all events you fetch exceeds 10 million rows in any date range, then sampling will happen.

Hope this helps! Let me know if you have any queries.