U.S. job openings tumbled in March to the lowest level in two years, an early sign the Federal Reserve's aggressive interest-rate hike campaign is beginning to cool the labor market. 

The Labor Department said Tuesday that there were 9.6 million job openings in March, a decline from the 9.9 million openings reported in the previous month. Economists surveyed by Refinitiv expected openings to fall to 9.7 million.

The Federal Reserve closely watches these figures as it tries to gauge labor market tightness and wrestle inflation under control.

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