The us stock market plunge on monday , 19 october 1987 sparked off a worldwide stock market slide . in hong kong , panic sale of stocks plummeted the hang seng index by 420 points , or 11 per cent in one trading day 美股于一九八七年十月十九日急跌,引發全球股市大幅下滑,港股出現恐慌性拋售,恒生指數于一夜間下跌四百二十點,跌幅達百分之十一,被稱為黑色星期一。