[laurus]

Assuming that the fall in aggregate demand will last for several time periods, in the absence of intervention, the companies lay off part of their workforce, since now they don't need to produce as much per time period. So now unemployment is up and overall output is lower. By cutting output, the companies don't necessarily have to cut prices. In short: the lack of intervention doesn't necessarily lead to a fall in the price level.

The point of saying that the Treasury bond accounts aren't counted as part of the monetary base while the reserve accounts are is that it doesn't really matter which account your money is in at the Fed. My original comment was pointing out that QE just moves reserves from one account to the other and that this has little effect on overall economic activity because lending by private banks isn't reserve constrained (MMT people do a good job explaining this as well).