The US stock market is now an Asian stock market

China's stock market rout has had investors looking eastward over the past few months.

That prompted Morgan Stanley analysts to ask: Are Asian markets now driving market movement in the economy that has historically led world indices - the US?

In a note last week, the analysts compared the S&P 500 to Japanese and Chinese indices over 126 trading days, and found that Asia's markets are now driving US markets to an unprecedented degree.

"The TOPIX is now more correlated with the S&P than at any time since at least 2000, including the financial crisis," Morgan Stanley analysts wrote.

"Meanwhile, the Hang Seng and Shanghai Composite returns are also at cyclical highs in terms of same day S&P returns."

The S&P 500 has no historical correlation with Asian market returns, Morgan Stanley wrote, but the prior night's returns of Asian equity markets now drive S&P returns.