Below is a chart of the Bloomberg World index's change in market cap since the start of 2011. Stocks worldwide have a total market cap of roughly $37 trillion at the moment. As shown, this is down $3.1 trillion since the start of 2011 and down $4.1 trillion over the past two months. Since the start of May, the world has lost roughly $3 trillion in market cap.
While the drop in stocks here in the US has been rough on investors, at least we're holding up better than pretty much everyone else. Below is a chart showing the percentage change in the S&P 500 and the Bloomberg World index since the start of 2011. As shown, the Bloomberg World index is down 7.57% since then, while the S&P 500 remains higher by 4.65%. It's important to note that the US makes up the largest portion of the Bloomberg World index, so that means that non-domestic stock markets have dropped even more than 7.57% over this time period. Up until last August, the S&P 500 and the Bloomberg World index were trading hand in hand, but since then, the US has significantly outperformed.