You bought a Picasso 2 years ago at an art auction and you paid $2 million for it. It's hung on your wall and now your tastes have changed to Chagal's. You take the Picasso to the auction house, but for the sake of this hypothetical, this auction is open to and attended by every single person on the planet that
might be interested in this sort of item.
And you get zero bids.
Is that $2,000,000 painting really worth nothing?
What if a well known Picasso was recently found to be a fake after a recent auction and the reason there are no bids is because there is now zero confidence that Picasso's that show up at auctions are genuine?
The above example is an extreme. So modify the situation to say there is a
rumor that someone has a fake Picasso, but that auction house is full of people who are still willing to buy yours and the information is out there and everyone is well aware that this painting sold for two million only two years ago.
Say the bids come in and stop at $1,000,000. Half what you paid. If this is your only way to sell this painting, it's value has just been declared by the most honest way known to man - an open outcry auction that clearly shows the price the market will bear - and your act of agreeing with that result is you marking to market that painting.
Bonds and other securities must be valued in this way or some related fashion so you know what you have. There is no other way to put a value on them.
So, if the banks were able to mark the market to a future price, would they have suffered the same losses we are seeing today? - The thing is, You have to know what it is worth today. It does not matter what it's worth in the future. How can you know for sure anyway?
Isn't that really arbitrary? If prices could go down, it almost sounds like the siutation could be made worse? - And it was made worse for many companies. That's basically what is happening now. The values of these various financial instruments is being radically revalued by the marketplace and it's causing turmoil.
Sounds to me like mark to market actually affords at least some consistency and transparency. Do I have all of this straight? -Yes and yes. It is important for the various entities that hold securities to properly value what they have.
The overwhelming number of debt securities out there do not trade on an exchange. They trade "Over-The-Counter"
This
Wikipedia page does a good but brief job of explaining this significant difference.
Bonds markets, unlike stock or share markets, often do not have a centralized exchange or trading system. Rather, in most developed bond markets such as the U.S., Japan and western Europe, bonds trade in decentralized, dealer-based over-the-counter markets. In such a market, market liquidity is provided by dealers and other market participants committing risk capital to trading activity. In the bond market, when an investor buys or sells a bond, the counterparty to the trade is almost always a bank or securities firm acting as a dealer. In some cases, when a dealer buys a bond from an investor, the dealer carries the bond "in inventory." The dealer's position is then subject to risks of price fluctuation. In other cases, the dealer immediately resells the bond to another investor.
Bond markets also differ from stock markets in that investors generally do not pay brokerage commissions to dealers with whom they buy or sell bonds. Rather, dealers earn revenue for trading with their investor customers by means of the spread, or difference, between the price at which the dealer buys a bond from one investor--the "bid" price--and the price at which he or she sells the same bond to another investor--the "ask" or "offer" price. The bid/offer spread represents the total transaction cost associated with transferring a bond from one investor to another.
This does not address the way all debt securities are traded, but it covers most of it.
It should be well remembered that one of the largest bond trading companies in the world was decimated on 9/11. Cantor Fitzgerald lost 2/3'rds of their employees (658 people) when the plane crashed into One World Trade Center. They have since rebuilt the company to its former strength.