SHANGHAI: China 's securities regulator vowed to step up market monitoring and crack down on excessive speculation, as the country's benchmark stock index hovered near a decade high with record turnover this week. The statement came after Chinese bourses said on Wednesday (Jan 14) that they would raise the minimum margin requirement for new borrowings to 100 per cent from 80 per cent, effective Jan 19, a move approved by the regulator and aimed at cooling the red-hot market. The Shanghai