How did Facebook detect "being Jewish" that users should not announce

In June 2017Number of users per month exceeded 2 billion peopleThen, on Facebook that became the world's largest influential SNS, data mining for extracting data that can be utilized in fields such as advertisements is analyzed by analyzing big data that records the user's actions in the service We are. In the past someoneFacebook knew that it was gay before family membersIt is obvious that Facebook sent a message related to religion also to users who did not publicly disclose that they were Jewish people, such as Facebook, which gained the ability to outperform people's "knowing power" It is becoming.

How Facebook knows you're Jewish - Sep. 21, 2017
http://money.cnn.com/2017/09/21/technology/business/facebook-rosh-hashanah-ad-targeting/index.html

The New Year of the Jewish CalendarRoche-Haschner"In the evening of 20th September 2017, some users logged in on Facebook celebrated the New Year" Happy New Year! All of us at Facebook wish you a sweet and happy new year. "(Happy New Year! New Year from Facebook There was a person who displayed a message saying "It's a celebration") on the screen. Many of the people who received the message were Jewish people, but it is calling people 's speculation that some people did not reveal themselves as Jews.

Software programmer Mauricio Sadikov who lives in Illinois, USA received a similar message from Facebook. But Mr. Sadikov did not mention confidence in Jew 's profile, such as Facebook profile. In response to this, Sadikov is posting on Twitter "I feel uncomfortable in many ways ... ... I have not mentioned about religion in my profile, but Facebook sent a Jewish New Year celebration" It is.

This is creepy in many levels ... I do not have any religion listed on my profile and Facebook just wished me a happy Jewish new year.

- Mau Sadicoff (@ tatonka)September 21, 2017

As the sole reminder, Mr. Sadikov is a Jewish festival several years agoHanukkahIt is presumed that "probably this is the cause"?

For Facebook and other SNS and Google's Gmail, etc., users can analyze contents posted by users, contents of e-mail, etc. on their computers, and track user's tastes by tracking actions and access history in the site I'm classifying it. The data obtained in this way is used for the purpose of displaying advertisements which are efficiently appealed by the user's interest, but this means that "Facebook wants to know what he wants The category of information that Facebook is gathering is from categories like "Millennial generation" to "from friends living overseas" and "away from family" "I lived there" and "It came back from a trip a week ago" and so on.

On Facebook, we are disclosing what kind of data we are using about advertisements, and the details on how advertisers are approaching the target audience are described on the following pages.

About Facebook advertisement
https://www.facebook.com/ads/about/?entry_product=ad_preferences

For Facebook, "Facebook sends a message based on a religious schedule to users living in a country where a particular religion is a majority, or living in a country where religious anniversaries are on holidays I am also sending a message to those who showed interest on that holiday. "The message that Sadikov's idea of" Posting about Hanukkah "was sent It is inferred that it became. A media professor at the University of Virginia Schwebaideidhanasan points out that the message sent by Facebook about Roche Haschner is a "new example showing how much Facebook is tracking us."

It is unclear whether Facebook is the first time Facebook sent a message on Roche / Hashaner, and Facebook does not answer CNN's interview. Professor Bernard Harcourt of Columbia University points out the possibility that this Facebook message is "a test to confirm the accuracy of the algorithm". This means that Facebook tracks that the user responds to the message "I am not a Jew, but thank you" or "How did you know that Facebook is a Jewish?" To determine the accuracy of the "Jewish decision algorithm". Although it is a theory that goes beyond guessing to the last, Mr. Harcourt points out that "When improving advertisements for Jews, algorithms improved by this series of tests may be useful."