Due to the economic downturn, housing prices in this area have been trending downward.

downward 是由 down（向下）加上后缀 -ward（表示方向）构成的副词，意思是"向下地、下降地"。 trending downward 表示"呈现下降趋势"，用来描述价格、数值等持续走低的情况。