Average Atlanta prices perfectly tracked the trajectory of the nation’s top 20 metro areas: up 5.7 percent from a year ago, according to a closely-watched report issued this morning.

But Atlanta’s prices – like the average of the top 20 – was unchanged in January, the S&P/Case-Shiller National Home Price Index.

“Home prices continue to climb at more than twice the rate of inflation,” says David Blitzer, chairman of S&P’s index committee.

Atlanta’s long-running struggle with low inventory – that is, a relative shortage of homes for sale – is part of a much larger trend, he said. “The low inventory of homes for sale – currently about a five-month supply – means that would-be sellers seeking to trade-up are having a hard time finding a new, larger home.”

For the month, today’s release of Case-Shiller index showed Atlanta roughly in the middle of the pack. Eight of the other big cities showed a decline of average prices during the month while 11 recorded an increase.

The biggest rise came in Los Angeles, where the month’s prices climbed 0.5 percent. Farther up the coast was the steepest drop: San Francisco prices fell 0.7 percent during the month.

When Case-Shiller factored in the normal seasonal patterns, Atlanta outperformed the usual January, rising 0.7 percent.

All the big metros saw prices up over the past year, with a dozen of them outpacing Atlanta’s increase, said Case-Shiller.

The fastest rise came in Portland, Ore., where average prices jumped 11.8 percent during the past year. Then came Seattle at 10.7 percent and San Francisco – despite the month’s decline – rising 10.5 percent for the year.