Stocks, oil, and metals prices all fell Thursday after a Chinese manufacturing index suggested that factory activity there is slowing. China has given the global economy crucial momentum since the financial crisis of 2008.
A separate survey measuring Europe's factory and service sectors also indicated contraction. As they sold higher-risk investments, traders moved money into Treasurys.
The price of the 10-year Treasury note rose 25 cents for every $100 invested, pushing its yield down to 2.27 percent as of 1:30 p.m. Eastern from 2.29 percent late Wednesday.
The yield rose earlier Thursday after the government said that new claims for unemployment benefits fell last week to a four-year low.