As they noticed the road go down, American buyers could have felt an unfamiliar sensation: nervousness. The S&P 500 fell by one other 4% within the week to March twelfth, leaving the world’s most watched stockmarket down by 9% since its current peak. The NASDAQ, dominated by tech companies, has fallen by 12%. It’s not fairly the daring new period of American development promised by Donald Trump in his election marketing campaign.