The stock market experienced significant turmoil on Friday as China retaliated against tariffs announced by US President Donald Trump.The S&P 500, Dow Jones, and Nasdaq all saw substantial drops, with the S&P 500 marking its worst week since the Covid-19 pandemic crash in 2020.Global markets also declined, with the UK's FTSE 100 experiencing its steepest fall in five years.The escalation of tariffs has heightened concerns about a potential global trade contraction and economic recession.