Even general news accounts presuppose an understanding of terms like “securitization,” “CDO,” and writedown.” So I thought I would provide my own translation.
Historically local banks took deposits from savings account customers and lent money to homebuyers. They paid 1% for the savings accounts and collected 6% on the mortgages, and the spread (5 percentage points in this case) was more than enough to compensate for any homebuyers who couldn’t pay their mortgages. (The numbers are illustrative only.)
Then, as any explanation of the subprime crisis says, banks started reselling and securitizing mortgages. But what does it mean to resell (let alone securitize) a mortgage?
To understand this, you have to look at it from the bank’s point of view. To them, a mortgage is a product. This product gives them a monthly stream of payments - about $1,000 per month for a 30-year, fixed-rate mortgage on a loan amount of $150,000 (numbers are very approximate), but that stream is not guaranteed; the homebuyer might not be able to pay (in which case they might have to renegotiate or foreclose, both of which are costly), or might pay the whole thing early. The price they pay for this product (this stream of payments) is just the loan amount; from their perspective, they are “buying” the stream of payments by paying you the loan amount. The lower the interest rate you get, the higher the price they are paying for your payments.
If Bank A resells your mortgage to Bank B, Bank B buys your payment stream from Bank A in exchange for a lump sum of money. Under stable market conditions, the lump sum that B gives A will be about the same as the lump sum you received from A (in which case A only makes money from various fees). You can also think of this as Bank B loaning you the money for your house, with Bank A acting as an intermediary.
Now, in practice, Bank B (or C, or D, …) is often an investment bank. And Bank B often securitizes your mortgage. This means they take your mortgage and combine it with many (thousands of) similar mortgages. If the mortgages are similar according to certain objective criteria - creditworthiness of borrowers, loan-to-value ratios, etc. - they can be treated as homogeneous. (Something similar happened with corn in the 19th century; certain standards were established for different grades of corn, and from that point bushels of corn from different farms didn’t have to be separately shipped and inspected by buyers, but could be poured together into huge vats.) Now you have a pool of, say, 10,000 mortgages, with about $10 million in payments coming in from borrowers every month. That pool as a whole has a price - the amount someone would pay to get all of those payment streams of that riskiness. In a securitization, the investment bank divides the pool up into many small slices - say 1,000 in this case. Each slice can be bought and sold separately, and each slice entitles the buyer to 1/1,000th of the payments streaming into that pool.
The price of these slices is based on current assumptions about the riskiness of those payments - the riskier those payments are perceived to be, the lower the price anyone will pay for a slice of them. The problem is that at the time those mortgages were securitized, the buyers assumed that housing prices could only go up, and therefore the payments were not very risky; when housing prices began to fall, many more borrowers became delinquent than had been expected. As a result, if you own a slice of that pool, you still own 1/1,000th of the payments coming in, but your expectations of how many payments will come in are much lower than they were when you bought the slice.
(A collaterized debt obligation is a securitization where the slices are not created equal. Some slices are entitled to the first payments that come in each month, and hence are the safest; some slices only get the last payments that come in each month, so when people start defaulting, those are the slides that lose money first.)
This brings us to writedowns and, eventually, to the subject of banking capital. Let’s say you are an investment bank and you paid $1 million for a slice of a securities offering (a pool). You put that on your books as an asset (in the world of finance, a stream of payments coming to you is an asset) valued at $1 million. However, a year later, that slice is only worth $200,000 (you know this because other people selling similar slices of similar pools are only getting 20 cents on the dollar). You generally have to mark your holding to market (account for its current market value), which means now that asset is valued at $200,000 on your balance sheet. This is an $800,000 writedown, and it counts as a loss on your income (profit and loss) statement. And that is what has been going on over the last year, to the tune of over $100 billion at publicly traded banks alone.
The next problem is that, over the last two decades, most of our banks have become giant proprietary trading rooms, meaning that they buy and sell securities for profit. Let’s say you start a bank with $10 million of your own money. That’s your “capital.” You go out and borrow $90 million from other people, typically by selling bonds, which are promises to pay back the money at some interest rate. Then you take the $100 million and buy some stuff (like slices of mortgage pools), which pays you a higher interest rate than you are paying on your bonds. Suddenly you are making money hand over fist. But then let’s say that housing prices start falling, securitized subprime mortgages start plummeting in value, and your $100 million in assets are now only worth $80 million. Since the value of your debt ($90 million) hasn’t changed, you are technically insolvent at this point, because your losses exceed your capital; put another way, the money coming in from your slices of mortgage pools isn’t enough to pay your bondholders.
According to some observers, this is where Fannie and Freddie were until they were bailed out by the U.S. government; by certain accounting rules, they had negative capital.
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