What happens when data are inaccurate, incomplete our outdated?
In other words, what happens when big data become bad data?

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The Eticas #BadDataChallenge wants to collect personal stories and reports about the social, ethical or economic consequences of bad and misused data.
Send your Bad Data experience and get your reward!

Data & Algorithms

Thanks to artificial intelligence, algorithms can be trained by and learn from data. But what an algorithm does depends a lot on how good the data is. Data could be corrupted, out of date, useless or illegal. In this way, bad data plays an important part of all kinds of decision-making processes and outcomes.


From banking to health to social services or education, bad data can have an important impact on our most fundamental rights. At the bottom of this page you’ll find a reading list filled with concrete examples of how bad data is already impacting society.

Bad Data prominent cases

New Coke
(incomplete data)

Facing competition from the sweeter-tasting Pepsi Cola in the mid-1980s, Coca-Cola tested a new formula on 200,000 subjects.

Cuts to health care based on algorithmic assessment (corrupted)

Similar to the case of disability payments in the UK, in the United States there have been a number of cases where radical readjustments were made to home care received by people with a broad range of illnesses and disabilities, after algorithmic assessment was introduced.

Disability payments in the UK (corrupted/biased data)

Starting in 2016, the number of appeals against decisions made by the Department of Work and Pensions on the basis of assessments made by the private, profit driven contractors working on its behalf began to increase dramatically.

Facebook and Cambridge Analytica (illegal/leaked)

Cambridge Analytica, a private company, was able to harvest 50 million Facebook profiles and use them to build a powerful software program to predict and influence election choices.

Incomplet or inaccurate personal data
(corrupted, out-of-date, useless)

Deloitte Analytics conducted a survey testing how accurate commercial data used for marketing, research and product management is likely to be.

CDC used bad data to judge DC water safety

In 2000, a problem with Washington, DC’s drinking water began when officials switched the disinfectant they used to purify the water. The switch was supposed to make the water cleaner. But the change also increased corrosion from the city’s lead pipes, upping the amount of lead in the water.

Predictive policing (biased, incomplete)

Police are increasingly using predictive software. This is particularly challenging because it is actually quite difficult to identify bias in criminal justice prediction models. This is partly because police data aren’t collected uniformly, and partly because the data police track reflect longstanding institutional biases along income, race, and gender lines.

Google’s Flu Trend

Launched in 2008 in the hopes of using information about people’s online searches to spot disease outbreaks, Google’s Flu Trend would monitor users’ searches and identify locations where many people were researching various flu symptoms. In those places, the program would alert public health authorities that more people were about to come down with the flu.

Bad Data en Visualizar 2018!

Our challenge was selected as one of the 6 projects of VISUALIZAR 18: Personal Data an international workshop that develops data visualisation projects.

It was set up in 2007 by José Luis de Vicente and it investigates the social, cultural and artistic implications of data culture, and it puts forward methodologies to make them more understandable and to open up avenues for participation and criticism.

This edition of Visualizar took place from Friday, September 21st to Friday, October 5th of 2018 in Madrid, at MediaLab Prado, a citizens’ laboratory that serves as a place of encounter for the production of open cultural projects.

As a result of this residence, and thanks to a collaborative work with volunteers and mentors of Visualizar, we did this visualization work for creating awareness and spread the knowledge on how bad data can affect our lives and our societies, a web page dedicated to Bad Data and its illness: The Bad Data Clinic.