From an article in the WSJ:
You may think your income is private information. But the credit bureaus may have your number.
And starting in February, your income—as estimated by the bureaus—may be used to help determine whether you get a new credit card.
Tuesday, the Federal Reserve issued its final rules related to last year's Credit Card Act, which, among other things, will require credit-card companies to consider an applicant's income or assets and current debts before approving credit. To provide flexibility, however, the Fed said that issuers can use "a reasonable estimate" of income or assets based on "statistically sound models."
In hopes of such a decision, the three big credit bureaus have been updating or rolling out products that seek to estimate consumers' incomes, based on information in their credit reports, such as the size and age of their mortgages or the size of their credit limits.
http://online.wsj.com/article/SB10001424052748703672104574654211904801106.html