IBM:

In 2012, Fortune ranked IBM the second largest U.S. firm in terms of number of employees (435,000 worldwide), the fourth largest in terms of market capitalization, the ninth most profitable, and the nineteenth largest firm in terms of revenue. Globally, the company was ranked the 31st largest in terms of revenue by Forbes for 2011. Other rankings for 2011/2012 include №1 company for leaders (Fortune), №1 green company in the United States (Newsweek), №2 best global brand (Interbrand), №2 most respected company (Barron's), №5 most admired company (Fortune), and №18 most innovative company (Fast Company).

Please answer a question about this article. If the question is unanswerable, say "unanswerable". What rank did Forbes have in terms of revenue in 2012?
unanswerable