Unlike iPhones, which are exclusively made by Apple, Android phones are produced by many different manufacturers. That’s made it much more difficult for Google—the company that designs Android software—to turn on device encryption by default. Many of the devices that run Android software have cheap or out-of-date hardware that can’t handle continuous encryption and decryption. Google recently required that all new Android devices encrypt device data by default—but exempted slower (and therefore cheaper) phones, making encryption a de-facto luxury feature.

(Apple sells its cheapest current iPhone for 400 dollars; new Android phones are available for as cheap as 30 dollars.)

That disparity affects most smartphone users in the U.S. According to recent data from comScore, a company that studies technology use, about 53 percent of the 198.5 million smartphone owners in the U.S. use Android phones. That’s about 105 million people.

And there are some clear patterns that separate the kinds of people that own Apple and Android devices. According to 2013 survey data from Pew Research, high-earning and highly educated people are more likely to own an iPhone. The survey also showed that African-American people are more likely to use Android phones.

The groups most likely to use Androids—low-income people and African-Americans—are also the groups that are under the most daily government surveillance, says Michele Gilman, a civil-rights lawyer and law professor at the University of Baltimore. She says this is a long-standing pattern that’s been amplified by modern technology.

“When encryption remains a luxury feature, those who are the most surveilled in our society are using devices that protect them the least from that surveillance,” said Christopher Soghoian, the principal technologist at the American Civil Liberties Union. He calls this the “digital-security divide.”

The lack of strong encryption in older and cheaper Android phones allows police to obtain user data more easily. When the contents of a phone are not encrypted, forensic tools that can extract those contents allow police to read all the phone’s data.

And the default messaging applications on Android phones are also less secure than Apple’s iMessage service. When Apple users text one another, their messages are encrypted end-to-end—that is, not even Apple can read them. (Apple can, however, read iMessage conversations that are backed up to its iCloud service.)

By contrast, Android phones come with SMS messaging by default, and most include Google’s Hangouts chat program. Neither of those tools is end-to-end encrypted, meaning that the companies that carry the messages from one phone to the other can turn over message contents to police if they’re required to.

Many Android phones also run outdated versions of the Android operating system, which leaves them more vulnerable to hacking. Even after Google releases patches for security holes, many phones don’t get those updates, because of the decentralized way that Android phones are sold.