Mr. Daco said federal workers might not spend as much as they would have absent a shutdown, and government contractors might not recoup all of their lost business.
A long shutdown would also delay the release of important government data on the economy, like monthly reports on jobs and inflation, by forcing the closure of federal statistical agencies. That could prove to be a bigger risk for growth than in the past, by effectively blinding policymakers at the Federal Reserve to information they need to determine whether to raise interest rates again in their fight against inflation.
The economy appears healthy enough to absorb a modest temporary hit. The consensus forecast from top economists is for growth to approach 3 percent, on an annualized basis, this quarter. But economists expect growth to slow in the final months of the year, raising the risks of recession if a shutdown lasts several weeks.
Diane Swonk, the chief economist at KPMG, said she expected G.D.P. to rise about 4 percent in the third quarter, and then slow to roughly 1 percent in the fourth quarter. She said a two-week shutdown would have a limited impact, but one that lasted for a full quarter would be more problematic, potentially resulting in G.D.P. entering negative territory.
“When you start nicking away even a tenth here or there, that’s pretty weak,” Ms. Swonk said.
A shutdown could also further convey political dysfunction in Washington, which could rattle investors and push up yields on Treasury bonds, leading to higher borrowing costs, Ms. Swonk said.
