PARIS Where will we live tomorrow? In the city, of course.

In fact, by 2050, two-thirds of the world's population will reside in what are already densely populated urban areas. But even more surely, we will exist amid a continuous stream of data. Over the last 20 years, information collected from everywhere — through social networks, geolocation technologies, temperature sensors, sound, cameras — has become known as big data. The monitoring of our societies — not to say the surveillance — is exponential in both industrialized and emerging economies, and it will only accelerate.

IT giant Cisco Systems estimated in a recent study that there will be three times more connected objects than humans on earth by 2017. Many researchers believe that a huge amount of increasingly refined data is likely to change our lives. The question is for what purpose.

Ten years ago, Walmart was already using predictive analysis to manage clothing inventory, depending on snowstorms or anticipation of scorching heat, for example. Today, algorithms allow for the analysis of the past to predict the future. Few economic sectors are exempted from the use of these new models.

Most smartphone owners have experienced (or suffered) targeted advertising after buying a book or airline ticket online. Netflix and Amazon capture the tastes of their customers, and develop offers of shows or products they might want before consumers know it themselves. Simply connect to a shopping center's Wi-Fi network, and you'll receive unsolicited promotions from different shops.

Trade isn't the only sector that benefits from these innovations. Insurance companies could be better equipped in the future to analyze risk, adapting their products and prices to specific profiles. Banks also benefit from these information mines, although the 2008 crisis proved that the rationality of mathematics lost out to erratic behavior motivated by greed.

Unexploited treasures

Of course, information can be collected and analyzed for purposes other than seeking profits. Without always being aware of it, governments, tax authorities, social security administrations, land registries, pension funds and employment centers all have access to underexploited treasures.

"The authorities are now wondering if making this data public could help to decentralize, increase transparency and overall improve their operations," says Steve Koonin, director of the Center for Urban Science and Progress at New York University.

In fact, New York has opened more than 1,300 databases to increase government transparency. It takes some effort to read the data detailing restaurant health inspections, car accidents, building permits, school math results and tax revenues, but the information is there for people who want to find it.

In the same vein, the Paris Open Data website holds a mass of scattered information. For those with the discipline to wade through the data, it can function as a magnifying glass for observing society, its habits and movements.

Combining these databases should push public services, traditionally organized without transparency, to exchange information and therefore increase the effectiveness of public health policies, education and transport. The city of New York, for example, has increased the evacuation of unhealthy and dangerous buildings by linking information about evictions, property taxes, complaints about squatters and reports of building damage.

In a study on the global impact of big data on both the private and public sectors, McKinsey Global Institute estimates that new data analysis systems could generate 3.4% of the gross world product. The studies are far less precise about the number of jobs this new ecosystem could create — or, at first anyway, destroy.