Very few iOS users are choosing to allow advertisers to track their browsing habits across apps on their iOS devices according to an ongoing survey from Verizon-owned Flurry Analytics.

The survey tracks how many iPhone users have opted to opt-in to sharing their unique Identifier for Advertisers (IDFA) with the apps they use since Apple changed from an opt-out to opt-in system last month with the launch of iOS 14.5.

Even when it was first announced, the change had advertisers concerned that the new rules would limit the effectiveness of in-app ads and hinder the revenue of ad-driven free-to-play apps and games in the process.

Analysts at Omdia predicted the short-term impact would look like a 17 percent drop in the in-app ad market for 2021, and thanks to Flurry's survey (found here) we're starting to get a look at how many people chose to share their IDFA following the change.

The data shared by Flurry here is updated day by day and the survey includes data from 2 billion devices based on the 1 million apps that use Flurry Analytics in some way. (More on methodology in the full blog here).

Currently, around 6 percent of users on iOS 14.5 in the United States have chosen to opt in to the new IDFA sharing system, either via individual prompts for each app or via a global toggle in their iPhone's settings. On a worldwide basis, that jumps to 13 percent.

While this gives a peek at how iPhone users are reacting to the change, the impact on the ad revenue side will likely take longer to see. Vocal opponents of the change like Facebook have said it'll decrease advertisers' ability to effectively monetize (specifically on its Facebook Audience Network advertising platform), and as such the company rolled out its own in-app privacy expainers in an effort to encourage more users to share their IDFA.