Atlanta’s average home price slipped slightly in the fall, as the region was outpaced by 15 of the 20 largest metros, according to a highly-watched national report.

Prices dipped 0.2 percent in October, although Atlanta’s average was still 6.1 percent higher than a year earlier according to Tuesday’s report from the latest report from S&P/Case-Shiller.

While prices have been decelerating from double-digit gains in 2014, Atlanta is smack in the middle of the pack for the year – 10th fastest. The 20-largest metros averaged an increase of 5.5 percent, while the national average for the year was 5.2 percent.

“Generally good economic conditions continue to support gains in home prices,” said David Blitzer, chairman of the index committee at S&P Dow Jones Indices.

And prices actually did better than they usually do during autumn’s normal ebb in housing demand: Adjusted for that seasonal trend, the Atlanta price was up 1.2 percent.

Still, the broad average masks some sharp divisions in the region: between north and south, between higher-priced and lower-priced homes and between the markets for different kinds of buyers.

For instance, a mismatch of supply and demand has opened up a larger-than-normal gap between the prices of new homes and those already-lived-in houses being resold.

“That gap is something like 25 to 30 percent for similar homes,” said Richard Whiteley, chief financial officer of FrontDoor Communities, a four-year-old builder. “That gap is way too high and it needs to close.”

The result is that prices of existing homes are rising faster than those of new homes, he said. “It makes sales tougher for us. It makes the gross margins tighter and makes us choosier when it comes to the land deals we make. We have to go out farther.”