So what is the effect of creating an extra $600 billion dollars of monetary base by having the Fed purchase $600 billion dollars of Treasury debt? The same thing that happens anytime any security is issued. Somebody has to hold it, and the returns on all other assets have to shift by just enough to make everyone in the economy happy, at the margin, to hold the outstanding quantity of all of the securities that have been issued. In practice, the only way you can get people to willingly hold $2.4 trillion in non-interest bearing cash is to depress the return on all close substitutes to next to zero. So short-term Treasury bill yields have been pressed to nearly nothing.
Of course, people also look at risky assets and ask whether they might be able to get higher risk-adjusted returns by holding those instead. In order to make people happy to hold the outstanding quantity of zero return cash, the prospective returns on other risky securities have also collapsed (securities are a claim to future cash flows - as investors pay a higher price, they implicitly agree to accept a lower long-term return). In my view, this has gone on to an extent far beyond what is likely to be sustained, but thanks to eager speculation, the S&P 500 is now priced, by our estimates, to achieve annual returns of just 3.25% over the coming decade.
Likewise, all of those securities yielding zero or nearly zero returns have to compete with commodities. Here, the markets have responded to the massive deficits of world governments by increasing their expectations regarding inflation. Now, if you're looking at a zero nominal return on money-market instruments, as well as expected inflation over time, it's natural to start hoarding commodities. See, if you expect your dollars to buy fewer goods and services in the future, and you're not earning interest to make up for it, you'd prefer to stockpile goods right now. This, of course, has created terrible problems for people in less-developed countries, who are experiencing soaring prices for food and fuel, but commodity hoarding was a predictable outcome of QE2.
The real question is how high commodity prices have to rise until people are indifferent between holding non-interest bearing cash, and commodities that are elevated in price. The basic answer is that commodity prices have had to "overshoot" the expected future level of broad consumer prices by enough that both cash and commodities can now be expected to suffer a negative real return as measured against a broad basket of consumer goods. This sort of overshoot is necessary to make people indifferent between holding one versus another, and it restores equilibrium in the face of the negative real return available on money market securities. As with stock prices, I believe that this has already gone too far, but the civil unrest in the Middle East has certainly worsened the situation over the short-term.
This is a critical point - commodity prices tend to swing by a much greater amount than consumer prices. You can easily get periods where general consumer prices are advancing, yet commodities prices are advancing slower or even falling. In my view, QE2 has provoked an "overshooting" advance in commodities prices, which has been necessary because the Fed is holding real interest rates at negative levels. In the face of moderately higher consumer price inflation, coupled with short-term interest rates at zero, the only way to get people to be comfortable holding that much cash is to make the prospective returns on every possible alternative just as bad.
Having discussed QE2, let's move on to the broader subject of "credit." Here also, there is a lot of confusion about how credit creation is related to real economic activity. My hope is that the following discussion will clarify some of these relationships. As usual, the best way to evaluate the merit of somebody's analysis is if they show you the data, so I'll also show you the data.