Congress has agreed and President Obama has signed the Student Loan Certainty Act of 2013 which will calculate interest rates based on the T-bill.
Beginning July 1, 2013 (they will retroactively go back) the new interest rates for loans disbursed between July 1, 2013 and June 30, 2014 will be:
3.86% Undergraduate Subsidized and Unsubsidized Loans
5.41% Graduate Unsubsidized Direct Loans
6.41% PLUS Loans (both Grad PLUS and Parent PLUS)
This means while undergraduate students are in-school their interest rate will be 3.86%; Subsidized loans the government will pay the interest rate, while the Unsubsidized Loans the interest is accruing at that same rate where the student is responsible for the interest.
Graduate students' loans will be accuring interest at 5.41% with the student responsible for the interest. As will the PLUS loan, the interest will accrue for the parent at rate of 6.41%.
These loans will have a new interest rate each July 1st, depending on T-bill, but the loan disbursed will have that interest rate for the life of the loan.