The economics of supply and demand is causing significant shifts in the sales prices of homes in Cobb County.

After peaking in June 2018 at $310,750, the median home sales price in Cobb dropped to $269,900 in September 2018, according to data from RE/MAX Georgia.

Median sales prices rebounded in the final months of 2018 to reach $283,500 in December before slipping to $260,500 in January, RE/MAX data shows.

The following two months both saw increases, raising the median sales price for homes in Cobb to $281,000 in March, according to RE/MAX. The latest data shows a slight dip from March to April to $280,000.

Glenn Field, a real estate agent with Marietta’s RE/MAX Pure, said the fluctuations in home prices are due to supply and demand. When the county has a low inventory of homes available and buyers are on the hunt for a new home, sellers are able to charge more for their homes, he said.

And summertime is the hottest time period for real estate agents, he said, because families are looking to get settled into a new home in time for the beginning of the school year.

“That’s a really hot time for real estate. And then it starts to die off a little bit in August because all the kids are back in school,” Fields said, adding, “In the summertime, that’s when you want to sell your house.”

National statistics track Fields’ view of the market. The number of days that a home on the market tends to spike in January and February plummet during the summer and climb again in the fall and winter, according to data from real estate website Zillow.

For example, the national average number of days a home was advertised on the site was 65 in June 2018 before climbing each month to reach a peak in February 2019 of 96 days. Then, the average started falling again.

These days, Fields said, the inventory of homes available for sale in Cobb is “right where it needs to be,” but there’s also new construction taking place in the county, which could offset the balance of supply and demand.

“There’s a lot of building going on right now, so that’s another thing that helps the inventory. It also tells you that if they’re building, the inventory is going down enough to warrant these homes being built,” he said, adding, “After this summer, I think we’re going to get a little drop, and then it might become a buyers market, say fourth quarter. I think there’s a good chance. … We’re going to have more inventory than we need.”

As a result, Fields expects prices to climb again this summer before falling in the fall and winter.