The US economy — the world's biggest — is accelerating, while China's — the world's second-biggest — is decelerating.

For 2015, Nuveen's Bob Doll predicts that the US economy will actually contribute more to global GDP growth than China's. This would be the first time that has happened in nine years.

"China is currently experiencing negative growth rates in imports and freight activity, and slowing growth in auto sales and electricity consumption," Doll says. "These trends are echoed in declining consumer confidence."

China is just one of the many emerging markets slowing down, a situation that has Doll predicting we could witness something that has been "unthinkable in recent times."

"We also think it is possible that US real growth will surpass that of the emerging-market economies for the first time since 1999," Doll said.

Check out this chart from Doll's new must-read presentation.