A private research group says that Americans' mood about the economy has darkened even further in January.

The Conference Board said Tuesday that its Consumer Confidence Index edged lower in January to 37.7 from a revised 38.6 in December. That's a historic low for the widely watched barometer, as shoppers worry about their jobs and watch the value of their homes and retirement funds dwindle.

It's also lower than expected. Economists surveyed by Thomson Reuters had expected a reading of 39. The levels in recent months have hit the lowest point since the index began in 1967.