In today's technological world we leave electronic traces wherever we go, whether shopping online or on the high street, at work or at play. That data is the raw material for a new industry of number crunchers trying to explain and influence human behaviour, as Stephen Baker explains in his new book The Numerati.
In the book, Baker meets the maths whizzes at the bleeding edge of this new way of doing business, politics, and even matchmaking.
You might be surprised at some of the things Baker's "numerati" want to know and can already find out about you. Read on for some examples taken from the book, and click here to read our full review.
Mountains of facts
Databases know more about you than you realise. A Carnegie Mellon University study recently showed that simply by knowing gender, birth date and postal zip code, 87% of people in the United States could be pinpointed by name.
Websites can collect huge amounts of data from users. Retailers, for example, can track our every click, what we buy, how much we spend, which advertisements we see - even which ones we linger over with our mouse.
Sites can easily access your entire web browser history, enabling them to try and guess your gender and other demographic information.
Some of the links that data can reveal are surprising, and profitable. Ad targeting firm Tacoda discovered that the people most likely to click on car rental ads are those that have recently read an obituary online, apparently planning their trip to a funeral.
The second largest group are romantic movie fans - they are suckers for weekend rentals perhaps trying to emulate the lovey-dovey escapes common in romantic fiction.
The business of data
Data is big business for the numerati. US firm Acxiom keeps shopping and lifestyle data on some 200 million Americans.
They know how much we paid for our house, what magazines we subscribe to, which books we buy and what vacations we take. The company purchases just about every bit of data about us that can be bought, and then sells selections of it to anyone out to target us in, say, political campaigns.
Much effort is expended finding new ways to gather data on people. A company called Umbria uses software to analyse millions of blog and forum posts every day, using sentence structure, word choice and quirks in punctuation to determine the blogger's gender, age interests and opinion. That knowledge can be a valuable tool to people launching new products, or politicians seeking votes.
Microsoft has filed patents for technology that monitors the heart rate, blood pressure, galvanic skin response, facial expressions of office workers, and even their brain waves.
The idea, the patents say, is to let managers know if workers are experiencing heightened frustration or stress. Given that the same technologies are used in lie detectors and to study human behaviour, it seems unlikely many workforces would quietly accept their boss introducing such a system.
Management by numbers
Such data makes it possible to manage workplaces more mathematically. A team at computing giant IBM is sifting through resumés and project records to assemble a profile of each worker's skills and experience.
Online calendars show how employees use their time and who they meet with. By tracking the use of cellphones, email and laptops it may even be possible to map workers' movements and social networks of each person.
The results might show that a midlevel manager is quietly leading an important group of colleagues - and that his boss is out of the loop. Maybe these two should switch jobs.
Health and safety
Number-crunching techniques can look after your home life too. At the Oregon Center for Aging and Technology in the US, researchers have computers that monitor every one of a user's interactions - every keystroke and mouse click.
The idea is that by watching a person's speed, vocabulary and sentence complexity over time it is possible to pinpoint the onset of cognitive deterioration - like dementia or Alzheimer's - long before more noticeable symptoms emerge.
The management of whole nations increasingly depends on the numerati, and not just because of their role in political campaigns.
After the 9/11 attacks, the CIA made large investments in statistical techniques to track known terrorists and even predict future ones, and has relied heavily on such techniques ever since.
One of the first pieces of software brought in was NORA, originally developed to reveal and track cheats and criminals working or staying as customers in Las Vegas casinos.