LOL. Anyone who says this is either ignorant, or deceitful. And LK isn't ignorant.
OK, let's try this again.
In 2003-5, rates were low but they began increasing in 2005. Ironically, in 2005, mortgage volume kept increasing DESPITE increasing rates? Why? Because rates were decoupled from one's ability to take out a mortgage. Why was it decoupled?
If you are a borrower your ability to take out a mortgage is dependent on your ability to repay it. Repayment willingness and ability is measured by credit score, income, and utility of the good you purchased.
In pre-2005, the credit boom was constrained to people who had good credit scores, verifiable income, and value in the good purchased.
Post-2005 that all was erased slowly, first through ARM, then to Option ARM, and to Liar Loans (low/no-doc). All of these eliminated the coupling of one's ABILITY to pay from one's ability to get a loan, regardless of interest rates.
Interest rates could have been 1,000,000,000% and it wouldn't have mattered because the 1-2 - year teaser ARM rate and 5-year Option ARM rate delayed the pain. Furthermore, the short-term nature of FICO scores and the no/low-DOC loans eliminated one's metric of long-term repayment.
Finally, the short-term nature of utility was the linchpin of everything. The utility of a house was to make money, provided money was made and the appreciation outstripped the short-term interest rate (you made more than you had to pay at minimum) then your utility was investment.
Thus, this considered all in one provided a full delinking of interest rates from the borrowing, destroying your rate foolishness.
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Now, on the lender side, your ability to extend loans was not dependent on interest rates, but of leverage. The buy/sell broker model for loans in wholesale lending was completely dependent on the ultimate purchaser getting enough leverage off of the entire mortgage. Traditionally the buyer/holder would either hold a loan until maturity or securitize it to to sell to maturity. However, every pool of mortgage securitized had lower-rated tranches that eventually accumulated until the required capital consumed a lender's balance sheet financing through equity and debt.
The interest rate of the lower tranches didn't matter, capital and financing did. Thus, what to do with the lower tranches?
Sell them!
How? Nobody will buy them, there's no offset for them, and nobody likes equity/mezzanine tranches enough, in volume enough, to make a difference. If there's 1,000,000,000,000 of subprime mortgages, and the lower tranches are 5%, that's 50bn of shit to get rid of. We don't have the balance sheet financing to deal with it and regulators will tell us that we have too many bad assets, so we have to come up with a way to get rid of it!
...hmmmm.....what to do?
Ohh, let's securitize those into CDOs, selling them as AAA securities. We'll claim modern portfolio theory and say that a diversified pool of investments will have non-correlated risk, regardless of whether the portfolio is correlated, if it is "diversified" then it is uncorrelated, right?
Right. So let's make CDOs to get rid of the lower tranches.
But wait, even if you can securitize 95% of subprime RMBS, and you can CDO 95% of the 5% of RMBS remaining, that still leaves 5% of 5%, or 50bps of RMBS. Eventually that 25bps adds up. If you have 1,000,000,000,000 of subprime mortgages, you have 2,500,000,000 of uber-shit to get rid of. Regulators will not like having too much uber-shit, so we must find a way to get rid of it.
Ohh, cool, we'll CDO the CDOs, CDO^2 is even cooler, thus we can now securitize the 5% of the 5% and only be left with 5% uber-uber-shit.
Now we're cool. We only have 125MM of total mortgage exposure from 1 TRILLION in exposure, we can easily deal with that.
You see, just like a borrower's ability to repay a loan wasn't dependent on interest rates, the lender's ability was only dependent on its ability to get rid of the loan as much as possible.
Thus ends the lesson and destroys your argument, now go fuck yourself and your loony ideas.