If you haven’t read Charles Duhigg’s article in The New York Times “How Companies Learn Your Secret,” set aside some time and read it (the piece is long).

Duhigg explores how companies gear their marketing towards people based on the personal information they collect. He managed to speak with Andrew Pole, statistician at Target, about the retailer’s predictive analysis and how the company found a way to market to mothers in their second trimester. A disturbing anecdote from the piece explains how Target knew about a young woman’s pregnancy before her father did.

Among the many insights in the story is that Target “assigns each shopper a unique code—known internally as the Guest ID number—that keeps tabs on everything they buy,” writes Duhigg. And you thought Big Brother was the government.

Pole, the Target statistician, told Duhigg:

“If you use a credit card or a coupon, or fill out a survey, or mail in a refund, or call the customer help line, or open an email we’ve sent you or visit our website, we’ll record it and link it to your Guest ID. We want to know everything we can.”

(Pole eventually clammed up, probably immediately after Target’s PR department got wind of his conversations with the media.)

Duhigg explains the demographic information linked to the Guest ID, which we’ve organized into this handy list:

1. Your age,
2. Whether you are married and have kids,
3. Which part of town you live in,
4. How long it takes you to drive to the store,
5. Your estimated salary,
6. Whether you’ve moved recently,
7. What credit cards you carry in your wallet,
8. What Web sites you visit.

He also mentioned that Target can buy the following data about you:

9. Ethnicity,
10. Job history,
11. The magazines you read,
12. If you’ve ever declared bankruptcy or got divorced,
13. The year you bought (or lost) your house,
14. Where you went to college,
15. What kinds of topics you talk about online,
16. Whether you prefer certain brands of coffee, paper towels, cereal or applesauce,
17. Your political leanings,
18. Reading habits,
19. Charitable giving, and
20. The number of cars you own.

Target wouldn’t tell the Times what demographic information it collects or buys.

Of course, collecting data as Target does isn’t new. Duhigg notes that “almost every major retailer” has a predictive analyst department charged with understanding customers’ shopping and personal habits. Target, however, has “always been one of the smartest at this,” a consultant told Duhigg.

Fascinating stuff. Read the full story here.