Business

‘Anonymized’ Credit Card Data Not So Anonymous, Study Shows

Published

11 years ago

January 30, 2015

In this May 9, 2012 file photo, a Visa credit card is offered at a store in New York’s Times Square. Credit card data isnt quite as anonymous as promised, a new study says. Scientists showed they can identify you with more than 90 percent accuracy by looking at just four purchases, three if the price is included and this is after companies wiped away personal details of credit card transactions. (AP Photo/Richard Drew, File)

SETH BORENSTEIN, Associated Press
JACK GILLUM, Associated Press

WASHINGTON (AP) — Credit card data isn’t quite as anonymous as promised, a new study says.

Scientists showed they can identify you with more than 90 percent accuracy by looking at just four purchases, three if the price is included — and this is after companies “anonymized” the transaction records, saying they wiped away names and other personal details. The study out of the Massachusetts Institute of Technology, published Thursday in the journal Science, examined three months of credit card records for 1.1 million people.

“We are showing that the privacy we are told that we have isn’t real,” study co-author Alex “Sandy” Pentland of MIT said in an email. His research found that adding just a glimmer of information about a person from an outside source was enough to identify him or her in the trove of financial transactions they studied.

Companies routinely strip away personal identifiers from credit card data when they share information with outsiders, saying the data is now safe because it is “anonymized.” But the MIT researchers showed that anonymized isn’t quite the same as anonymous.

Drawing upon a sea of data in an unnamed developed country, the researchers pieced together available information to see how easily they could identify somebody. They looked at information from 10,000 shops, with each data piece time-stamped to calculate how many pieces of data it would take on average to find somebody, said study lead author Yves-Alexandre de Montjoye, also of MIT.

In this case the experts needed only four pieces, three if price is involved.

As an example, the researchers wrote about looking at data from September 23 and 24 and who went to a bakery one day and a restaurant the other. Searching through the data set, they found there could be only person who fits the bill — they called him Scott. The study said, “and we now know all of his other transactions, such as the fact that he went shopping for shoes and groceries on 23 September, and how much he spent.”

It’s easier to identify women, but the research couldn’t explain why, de Montjoye said.

The study shows that when we think we have privacy when our data is collected, it’s really just an “illusion,” said Eugene Spafford, director of Purdue University’s Center for Education and Research in Information Assurance and Security. Spafford, who wasn’t part of the study, said it makes “one wonder what our expectation of privacy should be anymore.”

“It is not surprising to those of us who spend our time doing privacy research,” said outside expert Lorrie Faith Cranor, director of the CyLab Usable Privacy and Security Laboratory at Carnegie Mellon University. “But I expect it would be surprising to most people, including companies who may be routinely releasing de-identified transaction data, thinking it is safe to do so.”

Credit card companies and industry officials either declined comment or did not respond to requests for comment.

The once-obscure concept of metadata — or basic transactional information — grew mainstream in recent years following revelations by former National Security Agency contractor Edward Snowden. Those disclosures from once-top secret U.S. government documents revealed that the NSA was collecting the records of digital communications from millions of Americans not suspected of a crime.

The use of so-called “big data” has been a lucrative prospect for private companies aiming to cash in on the trove of personal information about their consumers. Retail purchases, online web browsing activity and a host of other digital breadcrumbs can provide firms with a wealth of data about you — which is then used in sophisticated advertising and marketing campaigns. And big data-mining was used extensively in the 2012 president election to win over voters or seek out prospective donors.

“While government surveillance has been getting a lot of press, and certainly the revelations warrant such scrutiny, a large number of corporations have been quietly expanding their use of data,” said privacy consultant and author Rebecca Herold. Studies like this show “how metadata can be used to pinpoint specific individuals. This also raises the question of how such data would be used within insurance actuarial calculations, insurance claims and adjustments, loan and mortgage application considerations, divorce proceedings.”

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Online:

Journal Science: http://www.sciencemag.org

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Seth Borenstein can be followed at http://twitter.com/borenbears

Jack Gillum can be followed at https://twitter.com/jackgillum

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Medi-Cal Cares for You and Your Baby Every Step of the Way

Across California, including Alameda and San Francisco counties, Medi-Cal is working to address those concerns by expanding and coordinating maternal health services so pregnant and postpartum people receive care that is respectful, comprehensive, and easier to navigate. From the first prenatal visit through a child’s first birthday, Medi-Cal provides coverage and support designed to protect both parent and baby.

Published

4 days ago

February 3, 2026

Oakland Post

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For many pregnant people, pregnancy brings a mix of both joy and uncertainty. Alongside excitement, there are questions about finding the right doctor, understanding what care is covered, and knowing where to turn for support after the baby arrives. For Black families in Alameda and San Francisco counties those questions are often compounded by long-standing disparities in maternal health outcomes.

These services are available to people who qualify for Medi-Cal. In California, eligibility is based primarily on income, household size, age, pregnancy status, disability, or other qualifying circumstances. Pregnant people qualify at higher income levels than non-pregnant adults and remain eligible through pregnancy and for 12 months after the pregnancy ends.

Importantly, pregnant people who qualify for Medi-Cal are eligible for full-scope coverage regardless of immigration status, including medical, behavioral health, dental, and vision services during pregnancy and the postpartum year.

A Clearer Path Through Pregnancy: The Birthing Care Pathway

The Birthing Care Pathway helps pregnant people understand what care they should receive and when, while supporting providers in delivering coordinated, culturally responsive services. It outlines key steps during pregnancy, including prenatal screenings, behavioral health check-ins, nutrition support, and preparation for labor and delivery.

For Black pregnant and postpartum people in Alameda and San Francisco counties the pathway emphasizes early prenatal care, shared decision-making, and connections to community-based programs that address medical needs and social drivers of health.

Doula Services: Support Before, During, and After Birth

Medi-Cal covers doula services for pregnant and postpartum members who qualify. Doulas provide non-medical emotional support, education, and advocacy during pregnancy, labor and delivery, and postpartum recovery. Research shows doula care is associated with reduced stress, improved birth outcomes, and increased breastfeeding success.

Covered doula services include prenatal visits, support during labor and delivery, and postpartum follow-up visits, in accordance with Medi-Cal benefit guidelines.

Care That Continues After Birth: The Postpartum Pathway

More than half of pregnancy-related deaths in California occur after childbirth, with Black families facing the greatest risks. The Postpartum Pathway defines the care pregnant and postpartum people who qualify for Medi-Cal should receive during the first year after birth.

The Pathway promotes a comprehensive postpartum visit within 12 weeks, ongoing primary care through 12 months postpartum, screening and treatment for postpartum depression and anxiety, breastfeeding support, chronic condition management, and referrals to community-based services.

Mental Health, Dental, and Vision Care Included

Medi-Cal covers perinatal behavioral health services for eligible members, including screening, therapy, counseling, and medication management when medically necessary. Services may be provided in person or through telehealth.

Pregnant and postpartum people who qualify for Medi-Cal also receive full dental benefits, including exams, cleanings, and medically necessary treatment, as well as vision care such as eye exams and eyeglasses.

Community Supports Through CalAIM

CalAIM (California Advancing and Innovating Medi-Cal) is a statewide initiative that strengthens Medi-Cal by improving care coordination and addressing health-related social needs.

Through CalAIM, eligible Medi-Cal members in Alameda and San Francisco counties may receive Community Supports such as transitional housing assistance, medically tailored meals, and help navigating social services.

How to Contact Medi-Cal in Alameda and San Francisco Counties

Pregnant and postpartum people who meet Medi-Cal eligibility requirements can get help enrolling, choosing a health plan, finding providers, or accessing doula and postpartum services by contacting the Alameda County Medi-Cal office at (510) 795-2428 or the San Francisco Medi-Cal office at (855) 355-5757 or calling the number on their Medi-Cal card.

Support at Every Step

Pregnancy and postpartum care should be clear, compassionate, and complete. Through the Birthing Care Pathway, Postpartum Pathway, doula services, behavioral health care, Black Infant Health, and Community Supports, Medi-Cal is working to ensure that eligible families in Alameda and San Francisco counties — especially Black Californians — receive the care and support they need to stay healthy and give their babies a strong start.

Ready to Learn More or Get Started?

Pregnant and postpartum people in Alameda and San Francisco counties can learn more about Medi-Cal benefits, enroll in coverage, or get help finding providers by contacting the Alameda County Medi-Cal office or San Francisco County Medi-Cal office or calling the number on their Medi-Cal card. Trained representatives can explain eligibility, available services, and next steps.