Key Highlights

● CoStar Group (CSGP) closed at $27.02 on Monday, down from $28.09, a steeper drop than the S&P 500.

● Its data showed third-quarter commercial Demand slightly negative, with net absorption expected to give back 2.7 million square feet.

● The 10-year Treasury Yield hit its highest level since 2007, raising borrowing costs for debt-financed commercial property.

● The average 30-year Mortgage rate climbed past a closely watched threshold for the first time since January 2025.

CoStar Group (NASDAQ:CSGP) fell on Monday, September 28, after its own research showed demand for Commercial Real Estate turning soft. The stock closed at $27.02, down from $28.09 on Friday, a steeper drop than the S&P 500, which lost 59.72 points to close at 7,683.69.

When the Data Company Becomes the Story

CoStar is best known as the leading provider of data, analytics and online marketplaces for commercial property, and it also runs residential listing platforms. The S&P 500, the benchmark of 500 of America's largest listed companies, includes CoStar. Because CoStar's clients are brokers, landlords, lenders and investors, a weak commercial property market can eventually weigh on its own business.

What the Numbers Showed

CoStar's data showed third-quarter commercial real estate demand was slightly negative, with net absorption expected to give back 2.7 million square feet. Net absorption is the change in occupied space: when it is negative, tenants are handing back more space than they are taking up.

CoStar's Commercial Repeat Sale Indices also pointed to weakness. The Composite index fell in August, and new deliveries of commercial space are projected to drop steeply from their peak in the fourth quarter of 2023. Fewer new buildings can eventually support rents, but in the near term it signals developers pulling back, which reflects caution across the industry.

Rates Made the Picture Harder

The data landed on a brutal day for anything linked to property. The 10-year Treasury yield hit its highest level since 2007, and the 30-year reached its highest since 2004. Commercial real estate is financed heavily with debt, so rising long-term rates push up borrowing costs, pressure valuations and slow transaction activity. Fewer deals and lower prices can mean less activity on the platforms CoStar runs, and slower hiring by the Brokers and landlords who pay for its data.

Housing was under similar strain. The average 30-year mortgage rate has climbed past a closely watched threshold for the first time since January 2025, and homebuilders and home-improvement retailers came under pressure. Futures now price a strong majority chance of another Fed hike in October, following September's increase under Chair Kevin Warsh.

A Risk-Off Tape

Breadth across the market was weak. On the Nasdaq, 2,218 stocks fell against 1,185 that rose, and new 52-week lows far outnumbered new highs. Allianz's Mohamed El-Erian said: "We would be having this yield discussion, even if oil prices were lower...we have an imbalance in longer-term demand for bonds and longer-term supply."

Property Data Will Meet a Rate Test

Rates remain the key variable for CoStar and the property sector. This week's calendar includes the Case-Shiller home price index, JOLTS Job Openings and consumer confidence on Tuesday, the PCE Inflation gauge on Wednesday, ISM Manufacturing and construction spending on Thursday and the September jobs report on Friday. Construction spending is especially relevant given CoStar's own projections for slowing deliveries.

The 10-year yield deserves close watching. If long-term borrowing costs stabilise, deal activity in commercial property could find a floor, but if they keep climbing, the soft demand CoStar's own data flagged on Monday may stay in focus for its clients and its shareholders alike.