NEW YORK (AP) -- Small business owners are growing more uncertain about the economy ahead of the presidential election and are reining in spending, according to a new survey.

The National Federation of Independent Business optimism index edged up 0.3 points in September to 91.5. But the uncertainty index rose 11 points to 103, the highest ever recorded.

While inflation is cooling and the pace of hiring appears solid enough to support a growing economy, small business owners till have a tougher time than bigger businesses holding onto workers and dealing with rent and other costs.

"Small business owners are feeling more uncertain than ever," said NFIB Chief Economist Bill Dunkelberg. "Uncertainty makes owners hesitant to invest in capital spending and inventory, especially as inflation and financing costs continue to put pressure on their bottom lines."

As they face uncertainty, small business owners are spending less. The net percent of owners reporting inventory gains fell four points to a net negative 13%, the lowest reading since June 2020. And 51% reported capital outlays in the last six months, down five points from August, the lowest reading since July 2022.

One bright spot is jobs. Thirty-four percent of owners reported job openings they could not fill in the current period, down six percentage points from August and the lowest reading since January 2021.

Despite signs that inflation is easing, it remains the top concern for small business owners. Twenty-three percent of owners said inflation was their single most important problem in operating their business, particularly in terms of higher input and labor costs.