Because credit contractions can emerge and spread rather quickly, the central bank must be prepared to act in an aggressive and timely manner to counteract their effects. And indeed, the Federal Reserve's policy actions since last August have been designed to ease the strains in financial markets and to counteract a projected weakening in economic activity.
So a key assumption underlying my 2008 projections is that economic activity is, in fact, highly vulnerable to a significant credit crunch. Because credit crunches can restrain economic activity through channels that are not fully captured by econometric models or historical experience, my forecast builds in a slower growth trajectory for consumer spending, residential investment, and non-residential investment than the model would have called for otherwise. These adjustments, of course, are only an educated judgment. A credit crunch could impose even more restraint on economic activity, presenting a downside risk to my baseline projection.