Just how powerfully intrusive is big data. A recent study published in the journal Science found that just four bits of information mined from a shopper's credit card could be used to uniquely identify ninety per cent of individuals. The credit card information was made up of ordinary, every day expenditures such as where the individual bought coffee or purchased a new sweater or pair of shoes.
Credit cards use was just as reliable at identifying someone as mobile phone records. An individual could be re-identified with "just a few more additional data points” even if some of the specifics were removed from credit card data, such as the general area where a purchase was made instead of the specific shop or if the time range was expanded to one day to 15. Interestingly women were more identifiable from metadata than men. Similarly people with higher incomes were also easier to identify.