British Prime Minister Boris Johnson imposed tighter restrictions as Covid-19 cases surge, measures which are likely to squelch economic activity - Copyright SPUTNIK/AFP Mikhail Metzel European and US stock markets dropped Thursday as traders tracked developments surrounding the Omicron coronavirus variant and fallout from the Chinese property crisis. The Dow ended flat but the Nasdaq and S&P 500 both fell despite data showing new filings for US unemployment aid dropped sharply last week, bringing them to levels not seen since 1969 for the second time this year. The indices’ declines ended a three-day rally that took Wall Street back near...