The deterioration in housing affordability is one key reason.

The chairman now sounds notably more worried than previously that house prices have risen too much and that the downturn could have a severe effect on the U.S. economy.

You've got seven quarters in which the homeownership rate basically has done nothing. It's fair to say that it's stagnating.

High margins are an inducement to invest more aggressively.

I'm not sure which form it will take -- maybe a lengthy period of subdued consumer spending or something more violent than that. But it's clear to me that households cannot continue to save 3 percent of their disposable income and grow debt at 10 percent per year.

Income figures ... were surprisingly low for December given the strong gains reported for the fourth quarter on Friday and the likelihood that bonuses would have boosted December gains.

The consumer numbers are certainly more important than normal.

The message is pretty clear here: they are quite determined to keep going.

nothing suggests that the Fed is close to a change in interest rates, in either direction.

They want to see how these first two rate increases go first. They are trying to straddle between not committing themselves to a third rate rise and not driving the stock market through the roof by saying they're done.