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Data Sheet—Big Data About Taxi Rides Sheds Unique Insights, But With a Privacy Cost

tax cabs in new York city.tax cabs in new York city.
New York City taxi regulators released data about millions of cab rides, providing useful research data but also raising questions about privacy.Timothy Clary—AFP/Getty Images

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If I tracked everywhere you traveled in a taxi, what could I learn about you? Aaron in for Adam today, contemplating some of the small data in a big data set.

The New York City Taxi & Limousine Commission a few years ago released a fascinating set of data, listing 1.1 billion separate taxi trips taken from 2009 through 2015. The data includes the GPS coordinates of the beginning and end of every trip, offering a detailed picture of where people traveled. Software developer and part time data cruncher Todd Schneider did some cool analysis when the set was released (including reality checking Die Hard 3: “could Bruce Willis and Samuel L. Jackson have made it from 72nd and Broadway to Wall Street in less than 30 minutes?”).

Now others are sifting the data searching for answers to all kinds of questions. University of Chicago grad student David Andrew Finer realized that the data could shed light on how Wall Street interacts with the Federal Reserve, especially around the critical times when the central bank is voting whether to raise or lower interest rates. The Fed’s decisions can move markets worth trillions of dollars, so Wall Street has a lot riding on the outcome of each meeting. But the Fed is supposed to operate in secret and not leak its moves in advance.

Finer decided to look at cab rides that traveled to and from the New York Fed and the headquarters of major banks. Sure enough, he found evidence that the number of trips jumped in the days around a meeting. The data could even be used to find when a rider picked up near the Fed got off at a destination that was the same time and place as another rider who had been picked up near one of the banks. The occurrence of these “coincidental drop-offs” at lunch time also jumped in the days around Fed meetings. “The timing and locations of the rides imply unofficial or discreet interactions, though this certainly need not imply any impropriety,” Finer concluded. Here’s a link to the PDF of the full study.

Correlation isn’t causation. Some further investigation, perhaps of emails and texts between people at the meetings, is needed. Finer refers to an earlier study that looked at stock returns around Fed meetings and suggested information was leaking.

Finer doesn’t name names, either. Is it Goldman Sachs or J.P. Morgan that had the most Fed-related taxi trips? But he certainly could. The data is so detailed that others have reverse-engineered the trips to show how easily the anonymous data can be de-anonymized. Some people tried to track celebrities based on known sightings and home addresses, while another attempt even purported to be able to identify which taxi driver were muslim based on activity during the five prayer times a day. Looks like it’s not just Facebook and Google that have collected worrisome data on us.

Aaron Pressman
@ampressman
aaron.pressman@fortune.com

NEWSWORTHY

Not again. Hackers stole 5 million credit and debit card numbers of people who shopped in retail stores of Saks Fifth Avenue and Lord & Taylor over the past year. Cybersecurity firm Gemini Advisory discovered the purloined numbers being shopped by the crooks. Hudson Bay, which owns both chains, said its online shopping sites weren’t breached.

Cheaper by the dozen. Most people who subscribe to Netflix, Hulu, and other Internet video services still subscribe to regular cable TV, too. But a growing cohort of cord cutters is relying solely on Internet services for their TV entertainment. Over 14 million households rely just on the Internet providers, almost triple the 5 million who did so in 2013, but still far less than the 90 million households subscribing to cable or satellite TV, according to the Video Advertising Bureau.

Food wars. Alibaba is buying control of food delivery startup Ele.me in a deal valuing the company at almost $10 billion. Ele.me, which means “hungry yet?” in Chinese, competes head on with Meituan Dianping, which is backed by Alibaba opponent Tencent.

Package wars. As it rationalizes its business this year under new CEO Dara Khosrowshahi, Uber has decided that its UberRUSH delivery service isn’t working. The ride hailing service will close UberRUSH—which operated in New York, San Francisco, and Chicago—at the end of June, the Wall Street Journal reported.

A better mousetrap. There’s a new way to get to the web sites you want to visit that may better protect your privacy. Startup Cloudflare introduced a domain name lookup service that can replace the DNS offered by Internet service providers. Cloudfare said its DNS, which matches a web site’s name typed in a browser with the site’s numerical network address on the Internet, would be faster and would not collect data about which sites customers visited.

FOOD FOR THOUGHT

Spotify’s unusual public stock offering on Tuesday won’t include offering any new stock or relying on Wall Street banks to price the shares. The tactics are the brainchild of the company’s CFO, Barry McCarthy, not CEO Daniel Ek, according to a profile by Recode’s Theodore Schleifer. The aim of cutting out Wall Street is a practical move, not any kind of an idealogical crusade for McCarthy, who previously served as CFO at Netflix but started his career trading mortgage-backed securities at Credit Suisse First Boston in the 1980s, Schleifer writes:

Spotify had to spend months walking regulators at the Securities and Exchange Commission through the details of the plan. And late last year, Spotify had to hammer out a way to mollify a pair of investors who had issued debt to Spotify that would only convert to equity when the company officially IPO’d. McCarthy and Ek found a way to soothe what at one point appeared to be a sticking point in the negotiations.

That has all led to to Tuesday, when Spotify shares will trade freely for the first time. It will be a big deal for Spotify, and it may be a big deal for future startups and the bankers who want to work with them.

Good luck getting McCarthy to say it’s a big deal to him. “I don’t think he’s trying to be the hero,” said one person close to the process. “He’s not an evangelist. He’s not really trying to change the world.”

IN CASE YOU MISSED IT

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Even as Bitcoin Languishes, Telegram Raises $1.7 Billion Ahead of Largest ICO Ever By Lucinda Shen

Snapchat Added an Egg Hunt in Time for Easter. Here’s How to Play By Lisa Marie Segarra

Facebook Employees Are Reportedly Deleting Controversial Internal Messages By David Z. Morris

BEFORE YOU GO

Despite fears that China’s Tiangong-1 space station could hit a populated region as it fell to earth, the space debris landed in the southern part of the Pacific Ocean on Sunday. Phew.

This edition of Data Sheet was curated by Aaron Pressman. Find past issues, and sign up for other Fortune newsletters.