A measure of US consumer confidence fell in December, a private research group said Tuesday, surprising analysts and signalling that the world's largest economy remains very fragile. The New York-based Conference Board said its consumer confidence index dropped 1.8 points to 52.5, after rising the previous month. Lynn Franco, director of research at the Conference Board, said households remained "cautious" about the economy and labour market. The drop came at the height of the holiday shopping season. Economists had expected the index to climb to 56.3, dpa cited a survey by Bloomberg News as saying.