The coronavirus wiped $3.18 trillion in market value from U.S. stocks this week, according to estimates from S&P Dow Jones Indices. The equity benchmark lost $203 billion in value on Friday, adding to its $2.997 trillion loss from Monday to Thursday, the firm's Senior-Index Analyst Howard Silverblatt told CNBC. The S&P 500 index has lost $3.58 trillion in value from its Feb. 19 high.