It may not be Big Brother from George Orwells 1984 but you might just be amazed at the information data miners know about you. As you travel around the internet you leave hundreds of clues about yourself, many of them so tiny that you wouldn’t think anything of them. But every one of them holds a clue to you and your lifestyle.

Author Stephen Baker takes a look into the the world of the men and women who take the seemingly random information and make sense out of it in his new book The Numerati.

What can be done with this information? An incredible amount. Who are the most likely people to click on an ad for a rental car? Believe it or not they are the same people who have recently read an online obituary. Why? Maybe they need to rent a car to go to the funeral. If you run a car rental agency you may never consider advertising on the local newspapers obituary page without that info.

It’s not just online that we leave a thousand footprints. Got a credit card? Nearly all, if not all, credit card companies sell the information they receive on your purchases. They don’t sell specifics but will sell a mailing list of people who bought a specific item.

Do you use a store courtesy card? Many stores, especially grocery but it’s moved well beyond just them, require a store card to receive the sale price on items. Ever wonder what happens to all that information? Do they really keep track of how much milk or bread you buy? Of course they do. And then they sell that info to other companies. If you buy 2 or more gallons of milk a week, it’s a pretty good bet you have children living with you. By knowing that, if I have a product to market to parents, you are a good choice.

Are you 50 or over? Then within a month of your turning 50 you probably got an invitation to join AARP. How did they know? They probably bought your information from your states drivers license bureau. The information is all out there, just waiting for someone to tie it all together for you.

Don’t use credit cards and store courtesy cards? It doesn’t really matter. A recent article in New Scientist claims that

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.

It may be that we don’t have to worry about the Big Brother from 1984, we may need to worry about The Numerati of 2009. It’s not the government who will know everything, it’s the data miners.

If you think that’s a little drastic, consider this. A recent study by Carnegie Mellon University showed that simply by knowing gender, birth date and postal zip code, 87% of people in the United States could be pinpointed by name.

Think about that next time some cash register clerk asks you for your zip code for their demographics.