Thursday, May 9, 2013

Sen. Warren's Bill and Why We Need More Math Majors in the Senate



Massachusetts Senator Elizabeth Warren released her first authored legislation today: The Bank on Student Loans Fairness Act.  Essentially, Senator Warren argues that the Department of Education should lower interest rates on student loans to 0.75% because that is the rate at which the Federal Reserve System lends to deposit holding institutions (referred to as “Big Banks”).  Without treading too deeply into the political malaise, I’d like to take a little time to address concerns I have with the logical framework that Warren is relying on.

The Discount Window is a mechanism through which the Federal Reserve makes secured overnight loans to banks in exchange for high quality collateral (in most every instance, loan assets).  The Fed charges a pre-set interest rate, called the “discount rate”, on these overnight loans, which is what Warren refers to when she references a 0.75% interest rate.  However, the Fed also institutes a discount margin on these overnight loans; that is, the amount the Fed will lend is capped by a loan-to-value ratio based upon the quality of the underlying collateral.  This pre-set loan-to-value ratio is called the collateral margin (or the “haircut”) and is readily available on the Fed’s website: Fed Collateral Margins.

The only Big Bank able to borrow at 0.75% from the Fed is the US Treasury.  This is because Treasuries have a very low collateral margin, whereas most every other asset has a meaningful margin that caps borrowing.  For example, US Treasuries have a collateral margin of 97%, which means that the Fed will lend me $97M in cash at 0.75% interest for every $100M in Treasuries that I bring to the discount window.  Alternatively, AAA rated corporate bonds have a discount margin of 95%, so the Fed would only lend me $95M for $100M in AAA corporate bonds.  The collateral margin for private student loans is 83% because the Fed perceives them as significantly more risky than either Treasuries or AAA corporate bonds (which, clearly, they are).  Given that Federal student loans default at a rate that is roughly 5x higher than private student loans, we would expect the collateral margin for Federal student loans to be significantly less than 83%: let’s generously say 70%.

The rate a bank charges borrowers is dependent upon the collateral margin because loans that have a lower collateral margin are more expensive to fund.  For example, an investor can take in $5M in equity and use that equity to buy $100M in AAA corporate bonds: $5M comes from the equity and $95M comes from the Fed discount window.  If the AAA bonds pay 2.5% interest, then the investor will collect $2.5M in interest each year and pay just $0.7M in interest on the loans from the Fed ($95M x 0.75%), which makes them an annual profit of $1.8M or a 35% return on equity.  That’s a great deal!  Unfortunately, great deals don’t last very long, so soon competitors will jump in and start buying up AAA bonds, which will drive down yields until they reach a stable return on equity.  Today, AAA corporate bonds are paying 2.0% interest, which (under the same conditions) would provide a return on equity of 25%. 

How much would the Department of Education be able to charge in interest if it were lending under the same terms as the Big Banks?  To figure that out, we simply reverse the calculation we did above.  The investor (the DOE) needs to make a 25% return on equity in order to match the returns of the AAA corporate bonds.  However, in this case the investor can only borrow up to 70% of the loan value from the Fed, which means it needs to bring $30M in equity in order to purchase $100M in student loans.  Thus, the investor would need to charge an interest rate of over 8.0% in order to match the returns of the AAA corporate debt.  The figure below demonstrates how this math works for several different types of loans (note that we are not factoring in certain other risks that would drive interest rates even higher).  So, if Warren were to get her wish, then student loan interest should actually increase rather than decrease under her proposed financing scheme.


Now, all this is not to say that Warren is wrong in her belief that student loan interest rates are too high or that the federal government is unable to rectify the situation.  The Department of Education does not need to borrow from the Fed in order to make loans: it can borrow directly from the Treasury.  Therefore, the Department of Education can charge any interest rate it wants: it could charge 5.0% or 0.0% or even negative 5.0%.  However, these lower interest rates would produce investor (taxpayer) losses that probably should be accounted for. A simpler solution to lowering student loan burdens might be to stop making them in the first place.

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