Posted tagged ‘MBS’

Why Stress Test Really Means Guesswork

March 15, 2009

Well, we’ve heard a ton about stress tests recently. Want some details on what a stress test entails? The Journal has some details about the tests here. Now, as much as I think GDP and unemployment are fine things to project forward for economists, let’s walk through the way one would use this to actually price an asset. Let’s start with something simple, like a 10-year treasury note (note that treasury bond specifically refers to bonds with a 30-year maturity). Here are all the components one would need to stress test the value of a treasury note.

  1. Characteristics of the note itself: coupon, payment dates, maturity dates, etc.
  2. What the yield curve would look like at the date you’re pricing the note.

Why would one need to know the shape of the yield curve (term structure of rates)? This is important, in order to “PV” the bond’s cashflows most accurately, one would discount each cashflow by it’s risk–the simplest proxy is to discount each cash flow by the rate of interest one would need to pay to issue a bond maturing on that date. For the government, this rate of interest is the point on the treasury yield curve (actually, the par zero curve) with the same maturity date. An example would be, if I were going to price a cash payment I will receive in two years, and the government can currently issue two-year debt at 5%, I should discount my cash payment (also from the government, since it’s a treasury note) at 5%. Treasuries are the simplest of all instruments to value.

Here’s an example, form the link above, of what a treasury yield curve might look like:

Normal Yield Curve

Now, it is completely and totally guesswork to figure out, given unemployment and GDP figures, what the yield curve will look like at any date in the future. Indeed, one can plug these projections into a model and it can come up with a statistical guess… But the only thing we know for sure about that guess is that it won’t be accurate, although it might be close. However, things like inflation will drive the longer end of the yield curve and monetary policy will drive the shorter end, so these certainly aren’t directly taken from the stress test parameters, but would need to be a guess based on those parameters. This is a large source of uncertainty in pricing even these instruments in the stress test.

Next, let’s examine a corporate bond. What would we need for a corporate bond?

  1. Characteristics of the bond: coupon, payment dates, maturity dates, special features (coupon steps, sinking funds, call schedules, etc.), where in the capital structure this bond sits, etc.
  2. What the yield curve would look like at the date you’re pricing the bond.
  3. The spreads that the corporation’s debt will carry at the date you’re pricing the bond.

Oh no. We already saw the issues with #2, but now we have #3. What will this corporations credit spread (interest/yield required in excess of the risk free rate) at the time of pricing? Will the corporations debt, which could trade at a spread of anywhere from 5 to 1500 basis points, be lower? higher? Will the corporations spread curve be flatter? steeper?

Here is a good illustration of what I’m referring to (from the same source as the figure above):

Credit Spread

There, the spread is the difference between the purple line and the black line. As you can see, it’s different for different maturity corporate bonds (which makes sense, because if a company defaults in year two, it’ll also default on it’s three year debt.. but the companies’ two year debt might never default, but the company might default during it’s third year, creating more risk for three year bonds issued by that company than two year bonds). It shouldn’t be a surprise, after our exercise above, to learn that the best way to compute the price of a corporate bond is to discount each cashflow by it’s risk (in my example above, regardless of whether the company defaults in year two or year three, the interest payments from both the three year and two year debt that are paid in one year have the same risk).

Well, how does one predict the structure of credit spreads in the future? Here’s a hint: models. Interest rates, however, are an input to this model, since the cost of a firm’s borrowing is an important input to figuring out a corporation’s cashflow and, by extension, creditworthiness. So now we have not only a flawed interest rate projection, but we have a projection of corporate risk that, in addition to being flawed itself, takes our other flawed projections as an input! Understanding model error yet? Oh, and yes unemployment and the health of the economy will be inputs to the model that spits out our guess for credit spreads in the future as well.

Next stop on the crazy train, mortgage products! What does one need to project prices for mortgage products?

  1. Characteristics of the bond: coupon, payment dates, maturity dates, structure of the underlying securitization (how does cash get assigned in the event of a default, prepayment, etc.), etc.
  2. What the yield curve would look like at the date you’re pricing the bond.
  3. The spreads that the debt will carry at the date you’re pricing the bond.
  4. What prepayments will have occurred by the date you’re pricing the bond and what prepayments will occur in the future, including when each will occur.
  5. What defaults will have occurred by the date you’re pricing the bond and what defaults will occur in the future, including when each will occur.

Oh crap. We’ve covered #1-3. But, look at #4 and #5 … To price a mortgage bond, one needs to be able to project out, over the life of the bond, prepayments and defaults. Each is driven bydifferent variables and each happens in different timeframes. Guess how each projection is arrived at? Models! What are the inputs to these models? Well, interest rates (ones ability to refinance depends on where rates are at the time) over a long period of time (keep in mind that you need rates over time, having rates at 5% in three years is completely different if rates where 1% or 15% for the three years before). General economic health, including regional (or more local) unemployment rates (if the south has a spike in unemployment, but the rest of the country sees a slight decrease, you’ll likely see defaults increase). And a myrid of other variables can be tossed in for good measure. So now we have two more models, driven by our flawed interest rate projections, flawed credit projections (ones ability to refinance is driven by their mortgage rate, which is some benchmark interest rate [treasuries here] plus some spread, from #3), and the unemployment and GDP projections.

I will, at this point, decline to talk about pricing C.D.O.’s … Just understand, however, that C.D.O.’s are portfolios of corporate and mortgage bonds, so they are a full extra order of magnitude more complex. Is it clear, now, why these stress tests, as they seem to be defined, aren’t all that specific, and potentially not all that useful?

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The Real Problem with the Citi Bailout

December 3, 2008

We all know that Citi was “bailed out” last week. However, as far as I can see, Citi’s is a unique situation for several reasons:

  1. The company was not taken over, and
  2. Management was allowed to stay on, and
  3. The government is shouldering losses coming from securities that are already identified.

Taken together, these leave a huge hole in this “living bailout” (I call it that because, obviously, Citi was in dire straights but was allowed to survive, essentially, as it existed before) that, obviously, Treasury never thought out (setting aside my prior concerns). I’ll put the problem into a single statement…

When taxpayers agree to pay for losses of a company that is continuing to operate, but the losses being referenced pertain only to specific assets, there are a huge amount of games that can played and the government has no way to stop or monitor what is truly going on.

As a matter of fact, as I write this the news of the G.A.O. report (PDF) on T.A.R.P. is making the rounds. One of the main criticisms is the lack of monitoring of bailed-out institutions. And those institutions don’t have explicit guarantees like Citi does. It is extremely surprising to me that, for example, there aren’t auditors or officials from Treasury meeting with traders and executives of Citi’s mortgage groups regularly. As a matter of fact, I would station some people on the trading desks where these assets are being managed to give status reports and monitor the situation. Further, Hank Paulson’s and Vikram Pandit’s interests are aligned here. Vikram shouldn’t want these assets languishing or Citi being accused of sitting on assets that might lead to a taxpayer loss in the future and Hank Paulson should want to know Citi still feels some obligation to minimize taxpayer’s exposure to losses.

Now, the question of what “games” can be played is the next natural question. Well, if I’m a trader, I mark my own position every day. In mortgages, there is little to no verification of these prices–the markets are so illiquid that only the people that trade the product know the actual value of a given instrument. This conflict, in general, is controlled for by the organizational structure: the person most likely to know the product as well as, if not better than, the trader is the trader’s boss. Obviously, the trader’s boss has little incentive to allow his employees to incorrectly mark the trading book because he can be held accountable. With this “living bailout” though, what incentive does Citi have to sell assets in a liquidity-challenged environment? If no pressure is applied from Treasury, and how can they apply pressure without being deflected if they aren’t “on the ground,” then why wouldn’t Citi just hold assets they currently view as having positive value? Citi likely has assets that are obviously going to go bad, in which case there is likely no way they can offload those assets (perhaps around, oh, say… $29 billion worth…), and assets they view as merely undervalued due to liquidity concerns. Why would I seek out a guarantee on further losses for assets I can sell today? If losses are guaranteed then what’s my downside in just holding illiquid assets?

Because Citi won’t absorb all the losses on the assets viewed as undervalued, those assets are worth more to Citi than others. And, as a trader that gets paid based on his/her personal P&L, I have every incentive to avoid losses that I view as not being inevitable and I have a defensible reason to not mark my position merely to the price I can sell it today. Another nuance comes from how traders actually mark their books…

  1. A trader buys mortgage bonds, loans, or any other security. The current profit or loss of that trade (we’ll call it “the bonds” or “the position”) is the purchase price and there is no net P&L.
  2. The trader then enters into another transaction that is considered a hedge for the position. This transaction could be buying credit protection, shorting treasury bonds, or any number of other possibilities. We’ll refer to these transactions as “the hedges.” This trade generates no net P&L.
  3. On an ongoing basis the position is marked “flat” to the hedges. This means that, dollar for dollar, any loss or gain in the hedges is added or subtracted from the original position so as to generate no net P&L. This isn’t perfect, but it’s theoretically very clean since the point of the hedges is to eliminate the risk in the position.
  4. Generally, a price movement in the position that isn’t reflected in similar price movements in hedges is marked manually–usually this takes place at month-end. However, if the original position is sold then the difference between the most recent marked price and the sale price will generate positive or negative P&L as well.

So here’s a good question: Why does a trader, now, have any incentives to hedge? A better question, though, is why would I mark my positions accurately versus hedges? Can’t I make the claim that all the gains in the position, as evidenced by losses in the hedges, should be taken as P&L but only 10% of the losses, as reflected by gains in the hedges, should be taken as P&L? Because the positions hedging the guaranteed mortgage positions are either derivatives or other products that likely aren’t also guaranteed this asymmetry becomes problematic. It’s not even clear that whatever scheme generates the most profits for Citi isn’t the correct way to account for the gains and losses of a typical hedged mortgage position in this atypical arrangement. I know that traders are asking these very questions. However, the possibility that taxpayers could shoulder costs while Citi also books profits whose existence depends on taxpayer-funded guarantees is troubling.

I don’t think anyone would disagree that this arrangement is complicated enough that a higher degree of oversight is required (and should be desired by all parties) to ensure that nothing improper is going on for the sake of taxpayers and Citi’s reputation. One thing we’ve learned from A.I.G. is that even if billions of dollars are at stake expenditures on the order of one hundred thousand dollars can become P.R. nightmares. Treasury should be auditing all of Citi’s mark-to-market procedures and setting standards to protect taxpayers (more so than non-“living” bailouts). Also, as I stated before, there is no reason that there shouldn’t be some sort of watchdog presence on the trading floors to ensure Treasury is keeping watch and being kept in the loop.

Fannie and Freddie: Some Facts to Keep in Mind

July 12, 2008

Well, Fannie and Freddie’s troubles have prompted this post (interrupting my work on the upcoming first installement of Build an Investment Bank). Basically, what I’ve bee hearing is that Freddie and Fannie are in trouble. Interesting. Here are some things to keep in mind about Fannie and Freddie…

1. Fannie and Freddie essentially securitize mortgage loans. This is complicated, but here’s the story in their own words:

Mortgage lenders … deliver pools of mortgage loans to us in exchange for Fannie Mae MBS backed by these loans. After receiving the loans … we place them in a trust that is established for the sole purpose of holding the loans separate and apart from our assets… Upon creation of the trust, we deliver to the lender (or its designee) Fannie Mae MBS that are backed by the pool of mortgage loans in the trust and that represent a beneficial ownership interest in each of the loans. We guarantee to each MBS trust that we will supplement amounts received by the MBS trust as required to permit timely payment of principal and interest on the related Fannie Mae MBS. We retain a portion of the interest payment as the fee for providing our guaranty. Then, on behalf of the trust, we make monthly distributions to the Fannie Mae MBS certificateholders from the principal and interest payments and other collections on the underlying mortgage loans.

(emphasis mine).

The essential point here is that Fannie and Freddie take on the entire risk of the mortgage defaulting in exchange for an ongoing fee (generally 50 bps per annum). The fee they charge for this type of transaction is small, generally less than 1/2 of 1/32nd of one percent of the principal balance of the loans they are guarenteeing. Also, Fannie and Freddie retain any risk of hedging their exposure. Part of this is meant to imply that the fees they collect offset the losses they expect to endure, but there’s also a lot of expense to hedging these exposures. I won’t pretend to understand all the complexities of this process, but they have to manage duration risk and interest rate risk (note that in mortgages, these are linked, but not exactly the same thing: lots of factors, including interest rates, affect a borrower’s decision to prepay their mortgage and changes in interest rates affect the future cashflows from fees). This is more art than science as it is very dependent on odd accounting rules and complex models–models that are a best guess at an uncertain future. Read their risk management section (and keep in mind that O.A.S. models are just lots of iterations run over another set of models… so, two layers of models… and we know how good those have performed) or this OFHEO report, specifically the sections on risk (Model Risk especially). The report I just linked to goes into, in depth, the various risk, accounting, and hedging issues at “the Enterprises.”

2. Fannie and Freddie are one of the largest, if not the largest, buyers of mortgage product. They buy their own mortgages (ones they have seen securitized) and hedge their massive portfolios. They issue bonds at extremely cheap levels to fund these activities. One former treasury official seems to think that this huge funding advantage seems to have translated into a bit of reckless purchasing on the part of the agencies. They even tout this–going back to the Fannie filings, we learn the following:

The U.S. Congress chartered Fannie Mae and certain other GSEs to help ensure stability and liquidity within the secondary mortgage market. In addition, we believe our activities and those of other GSEs help lower the costs of borrowing in the mortgage market, which makes housing more affordable and increases homeownership, especially for low- to moderate-income families.

(emphasis mine).

How noble! They lower the cost of a morgtgage by, well, buying lots of them and lowering rates. Why do they buy so much? so they can lower rates. Easy to understand, right? The reason they do this is to help increase home ownership. Interesting, then, that their business volume in 2007 had 11% investor properties or second/vacation home (see table 41, here). Also interesting, then, that 32% of their business was lending for cash-out refinancings (same table)–those don’t seem to be helping home ownership, and actually reflect a higher risk segment of mortgage loans. So, Fannie and Freddie own a huge amount of their own product, which is notoriously difficult to hedge, have bought a lot of product fore the sake of buying, and seem to have a portfolio composition that is slightly different from it’s purpose… Well, holdon. It gets even better!

3. Fannie and Freddie were the largest buyers of sub-prime mortgage bonds and commercial mortgage-backed securities. Look at any securitization, look at the AAA-rated portions, and if there is a class that is all loans considered “conforming balance” or have amounts that generally conform to the agencies’ maximum loan size limits, then you know those were purchased by an agency. At the end of 2007 Freddie owned $100 billion of these sub-prime securities (according to OFHEO, page 43, pdf) where 21% of loans were 60+ days delinquent. Fannie Mae has about 13% of it’s portfolio, which was an average of $725 billion during 2007 (from their filings), or $94 billion. Now, if regulators understood these products, they would understand that securitizations are structured in a way that Fannie and Freddie could be at risk for a decline in value of their own securities that occurs from the performance of the other assets–the ones that have nothing to do with their goals and charter. I would even challenge anyone who thinks that congress would agree with the programs that Fannie and Freddie use to support their mission … I’ve been on calls with people discussing how Fannie and Freddie merely need to be able to claim something passed the most cursory of tests to take on a $1+ billion loan. Providing the opportunity to afford housing to credit worthy indivisuals has nothing to do with buying CMBS and sub-prime RMBS.

What does all this point to? Seemingly a massive amount of “mission creep” for the agencies that lead them to be over-levered, in increasingly risky products, and in an accounting and hedging nightmare.