Global stock index has lost $2 TRILLION this year

Global stock markets have endured a rough start to 2016. One metric shows just how brutal a year it has been so far.

The S&P Global Broad Market Index, which tracks global stock performance, has lost $2.23 trillion in market value this year. For perspective, the total trumps estimated U.S. student loan debt of more than $1 trillion and would represent roughly 12 percent of U.S. government debt.

Stark drops in Chinese markets, sliding crude oil prices and geopolitical concerns, among other factors, have contributed to selling across the globe.

A trader on the floor of the New York Stock Exchange, January 7, 2015.

Brendan McDermid | Reuters

The suffered its worst four days to start the year ever this week, falling nearly 5 percent. The Dow has also slid more than 5 percent.

The Shanghai composite has plunged 15 percent this week, while the German DAX has lost 7 percent. Twice this week, Chinese trading was halted when drops of more than 7 percent triggered a circuit breaker.

The health of Asian markets overnight, as well as the U.S. nonfarm payrolls report Friday, will help determine how stocks will close the week.