Alphabet Inc.'s (GOOG  ) (GOOGL  ) Google's map usage on iPhones has seen a significant decline, with the company recovering just 40% of its former mobile traffic since Apple Inc. (AAPL  ) switched to its own mapping service.

What Happened: During the ongoing antitrust trial against Google, Michael Roszak, the company's vice president for finance, revealed critical insights into the impact of Apple's move to replace Google Maps with its native app on iPhones.

In a June 2020 email presented as evidence, Roszak shared data that shed light on the extent of the decline in Google Maps usage among iPhone users, reported Bloomberg.

"Almost 2 years later we were at ~40% of the prior peak (and assumed the actual loss was greater since Apple Maps usage was also growing across this time)," Roszak stated in the email.

The chart illustrating Google Maps usage on iPhones was not disclosed publicly.

Roszak stated that Google does not keep data on how many users change their search default settings on browsers or mobile devices, and the Apple Maps transition serves as just one data point in estimating user behavior in response to changes in default search settings, the report noted.

Why It's Important: The U.S. Department of Justice has alleged that Google unlawfully maintained a monopoly over online search by securing default status on web browsers and smartphones, with its most prominent contract being with Apple.

This contract, in which Google allegedly pays Apple a share of advertising revenue for being the default search engine on the Safari browser, has faced scrutiny, with the Justice Department saying that it ranges from $4 billion to $7 billion in payments made by the tech giant to the Tim Cook-led company in 2020.