。
Today's stock prices are trending downward.
Literal
Today [possessive-の] stock-price [topic-は] falling tendency.
株価 ('stock price') is 株 ('stock/share') + 価 ('price'). ~気味 (ぎみ, 'tendency toward, slightly') is a useful suffix indicating a mild trend — 下がり気味 ('tending downward'), 風邪気味 ('coming down with a cold'). A financial-news register sentence.