Earlier today we once again noted how much the US has been outperforming the rest of the world in 2013. This outperformance has pushed the percentage of total world stock market cap that the US makes up to its highest level since the start of the fourth quarter. In the fourth quarter of 2012 when US markets were roiled by the fiscal cliff negotiations, the US lost a pretty significant portion of world market cap, but it has now gained all of its lost ground back. As shown below, the combined market cap of all the stocks in the US now makes up 33.63% of the world's market cap (using Bloomberg data).
Below is a longer-term chart of the US' percentage of world market cap. The first decade of the 21st century was a time when the rest of the world gained significant ground on the US as the "World is Flat" theme took hold. The first quarter of the second decade of the 2000s has seen a reversal of this trend, however. After bottoming in 2010, the US has been steadily increasing its share of world market cap. Only time will tell if this trend holds for the remainder of the decade.