A new survey shows employers statewide continue to gain confidence in the prospects for an economic recovery, but expect business conditions to remain challenging for some time to come.

The Associated Industries of Massachusetts said its monthly Business Confidence Index rose a half-point to 40.6 in August. The index has risen in five of the last six months after sinking to an all-time low of 33.3 in February.

The index operates on a 100-point scale, with any rating under 50 seen as more pessimistic than optimistic. The highest rating ever recorded was 68.5 in 1998.

Raymond Torto, who chairs the group’s Board of Economic Advisors, sees a slow but steady improvement in employers’ overall outlook. But he says many do not expect significant economic changes until mid-2010.