Here are the most popular emoji on iPhones in the United States, according to Apple (AAPL)

Apple released a list of the top emoji used by English speakers in the United States.
"Face With Tears of Joy" is the most used emoji by a lot — although Apple didn't release statistics that give a sense of how often they're used.
The list was released as part of a new paper describing a statistical technique Apple uses called "local differential privacy."

Americans love the crying face emoji that's used to convey hearty laughter, Apple revealed on Friday. The "Face With Tears of Joy" beat out other popular emojis, including the face with heart eyes, rolling eyes, and a skull.

The chart Apple released was included in a paper describing "local differential privacy," a technique that Apple started to use last year to collect data without compromising user privacy.

Basically, the idea is Apple can add random noise to individual user data to protect privacy. When Apple collects a lot of data points, it's able to control for that noise and gain insights into a huge group without compromising individual privacy.

So that's how Apple is able to rank the most used emojis on iPhones and Macs without specifically spying on the emojis an individual user is typing.

Here's how Apple describes the technique:

The differential privacy technology used by Apple is rooted in the idea that statistical noise that is slightly biased can mask a user’s individual data before it is shared with Apple. If many people are submitting the same data, the noise that has been added can average out over large numbers of data points, and Apple can see meaningful information emerge.

Apples ranking is solid

Apple's list looks pretty close to other top emoji rankings, with one exception, said Jeremy Burge, emoji expert and founder of Emojipedia.

"Overall Apple's emoji rank looks pretty believable, but the skull stands out as being 7th in Apple's list, but rarely even top 20 when using public data," Burge said. "Are people using the skull differently in private conversations compared to public data sources like Twitter? That's what the data might suggest."

"The other emojis in Apple's list look pretty close to what we see on Emojipedia and sites like EmojiTracker," he continued.

The fact that Apple's emoji ranking is close to other rankings suggests its differential privacy technique is working. Apple also uses differential privacy to collect other statistics, including websites that drain your battery, websites that crash your browser, and health data.

The paper published on Friday also describes the specific math and equations used in Apple's implementation.

If you're curious about what data you're sending to Apple, you can look it up on your iPhone through Settings > Privacy > Analytics > Analytics Data, and you can control whether you send information to Apple in System Preferences.

Read Apple's full paper on differential privacy here.