A measure of optimism among small business owners continues to decline on less upbeat expectations for improving conditions and persistent concerns about inflation.

The National Federation of Independent Business reported its Small Business Optimism Index fell a half point to 90.8 in September. The index has remained below its 49-year average of 98 for 21 consecutive months.

“Owners remain pessimistic about future conditions, which has contributed to the low optimism they have regarding the economy,” said Bill Dunkelberg, chief economist of the NFIB. “Sales growth among small businesses has slowed and the bottom line is being squeezed, leaving owners few options beyond raising selling prices for financial relief.”

The NFIB bases the index on monthly surveys of members of the small business advocacy group, most of them small business owners. Between August and September, four of 10 components of the index retreated, five advanced and one remained unchanged.

The proportion of NFIB members who responded to the survey upon which the September index was based who expect the economy to improve fell another six points. At a net negative 43 percent, the level remains at a recessionary level.

A net 24 percent of members reported plans to increase capital outlays, unchanged from August. A net 5 percent said they consider now a good time to expand, down a point.

The share of members who said they expect increased sales fell a point. At a net negative 13 percent, more anticipated decreased sales.

Expectations for earnings increased a point, but only to a net negative 24 percent. Among those reporting lower profits, 29 percent attributed the trend to lower sales, 20 percent blamed rising materials costs and 15 percent cited higher labor costs.

A net 18 percent of members reported plans to increase staffing, up a point from August. At the same time, though, 43 percent also reported hard-to-fill job openings, up three months. A net 23 percent of members said they plan to raise compensation in the next three months, down three points.

The proportion of members who said they plan to increase inventories fell a point to a net negative 1 percent. The share of those who said current inventories are too low rose a point to a net negative 4 percent.

Asked to identify their single most important problem, 23 percent cited inflation and 23 percent cited the quality of labor. Another 13 percent cited taxes. A net 41 percent of members reported raising average sales prices.