I think the potential issue here has to do with how Analytics identifies visitors. Using the mid is actually the 3rd key in priority that is used to identify a visitor. Just because an mid is present does not mean, that the mid was the key used to identify the visitor. I understand the logic you are going by, if an mid is present then it should be a UV but it isn't quite as simple as that. If any users came before the visitor id service was implemented then they were idenfied by the aid instead of the mid. Even though both are present. Here's the priority used to identify visitors: https://marketing.adobe.com/resources/help/en_US/mcvid/mcvid-analytics-order-of-operations.html You could confirm this via a data feed/raw data by looking at all the visitor Id fields. There's a bunch of them visid_high, visid_low, post_visid_high, post_visid_low, mcid_high, mcid_low, visid_type etc. The post_visid_high/low are the identification key. That is populated from the visid_high/low (which is an aid) or from the mcid_high/low (which is the mid). The visid_type tells you what kind visitor it was basically how the post was generated. That's where I would start.
Without looking at the raw data, it's pretty hard to determine what may be causing this. Do you have grace period turned on? If so, there may be some discrepancy between unique visitors and "mid"s.
I would recommend the following:
Pull raw data for a specific time period
Ensure that data is all from a single source (your website)
Ensure that data does not have "aid" (Analytics ID) values for your visitors
Ensure each hit has a value in the Evar that you'd expect to see the 'mid'
Run a report in Analytics for that same time period
See if you get the expected results
I'm thinking you've got some data that isn't matching up correct. This could be caused by a number of different issues. Using data that has a mix of aid and mid values being used to identify the visitors is most often the cause.
Yes, if you've deployed the MCID service, each unique visitor should have a 'mid' associated with them. As for storing it in the eVar2, that would be something custom setup on your end. You may want to check the hits showing as "none" to see if they are coming from another source (mobile app, API, ect...).
Thanks for the reply Jantez. I deployed MCVID long back(before Sep2016). And, verified the metrics only for last 3 days. By the way, i don't see any "none" if i choose the metrics as "Pageviews". None appears only for unique visitors. Not sure, it is advisable to use Unique visitors as the metrics. Here is my understanding on the MCVID value. For every unique visitors, there should be 1 Mid value and that should be recorded/stored in eVar2 report. Correct? for eg: if we got 3000 unique visitors for 3 days then we should see 3000 mid row values in the report. Am i missing anything here?
When did you deploy the Marketing Cloud ID service? Does the date range in your report include dates prior to deploying the ID service? If so, that could be one cause of seeing "none" in the reporting.