Goldman Sachs Group got hit with a case of the holiday blues. The worry for investors is that the weak fourth quarter signals a longer-lasting funk.

Net profit for the quarter fell 50% from the prior year, to $2.4bn, as revenue from its usual engine for growth-the fixed-income, currency and commodities business-also halved to $1.6bn. That was partly because of a usual seasonal slowdown in trading, but also from investors growing wary as interest rates turned abruptly.