The biggest rout in commodities since the global recession may be a sign that the fastest U.S. inflation in three years is peaking.

The Standard & Poor's GSCI Index of 24 commodities entered a bear market last month after sliding more than 20 percent from a two-year high in April, on concern that slower growth will cut demand. A slump in the gauge from a 2008 record preceded a drop in inflation, while a 2009 rebound caused the consumer price index to climb. Raw materials fell 12 percent in September as the CPI rose 3.9 percent from the same month a year earlier, the most since 2008.

"There is a sense that headline inflation is receding," said Stephen Stanley, the chief economist at Pierpont Securities LLC, a government-bond broker in Stamford, Connecticut. "Things have been a little more tame the last few months than they were earlier in the year, when you had this relentless push higher, in energy prices especially."