Why a business may not ahieve its targeted gross margin?

Why a business may not ahieve its targeted gross margin?
Cost of goods sold may have been higher than expected or salesprices may have been lower than expected. Remember the Gross marginis sales less cost of goods sold. Say $100-$50=$50 gross margin(50%). If they only sell for $90 instead of $100 the margin wouldbe $90-$50=$40. Or if costs were higher you might have ended upwith $100-$60=$40. Either one would reduce the gross margin.