The risks of such a database were highlighted last year when the leftwing investigative journalism website Pro Publica said it had “obtained a vast trove of Internal Revenue Service data on the tax returns of thousands of the nation’s wealthiest people, covering more than 15 years.” If this proposal had been in place at the time, Pro Public might also have data on bank credits and debits.
In other words, even if the IRS cannot effectively analyze the data, just the fact that it has it might persuade Americans to report income that might have gone unreported.
Yellen claims in her letter that although the IRS would receive bank information on Americans of all incomes, the proposal is aimed at collecting more taxes from the wealthy.