By Ellie Ismailidou, MarketWatch

Weakest-ever reading on wage growth sent 10-year yield to a three-week low

Treasury yields plummeted on Friday, finishing at the lowest level since July 8, after the Labor Department said U.S. employees' wages and benefits rose a record-low 0.2% in the second quarter.

Friday's moves wrapped a monthly rally in which Treasury yields recorded their largest three-week decline since April 3 and their largest monthly decline since January, pushed lower by falling commodity prices and a decline in inflation expectations.

Read: July's Treasury rally was fueled by market turbulence (http://www.marketwatch.com/story/julys-treasury-rally-was-fueled-by-market-turbulence-2015-07-31)

The yield on the 10-year Treasury slid 6.1 basis point on the day and 12.8 basis points over the month to 2.207%, according to Tradeweb. That is only 0.1 basis point above the 2.206% mark hit on July 8. The yield last closed below 2.206% on June 1.

The yield on the two-year note , fell 5.45 basis points to 0.676% on the day but rose 3.9 basis points over the month. And the yield on the 30-year bond , declined 4.8 basis points on the day and 26.3 basis points over the month to 2.914%.

On Friday, the wage growth number, the smallest gain in the 33-year history of the report (http://www.marketwatch.com/story/us-employment-cost-index-decelerates-sharply-in-second-quarter-2015-07-31), was interpreted as an indication that the labor market may not be as healthy as the unemployment rate suggests. That in turn could lead the Federal Reserve to push back its first interest-rate increase (http://www.marketwatch.com/story/sharp-deceleration-in-employment-costs-gives-fed-a-reason-to-delay-rate-hike-2015-07-31) in nearly a decade.

The weak reading suggests the U.S. economy is still far from reaching the Fed's 2% inflation target, said Kathy Jones, chief fixed-income strategist at Schwab Center for Financial Research.

"With falling commodity prices weighing on the market, the only support for inflation was supposed to come from the wage front. Now even that comes into question," Jones said.

While U.S. stocks moved slightly lower (http://www.marketwatch.com/story/us-stocks-sp-eyes-2-rise-for-month-but-month-end-volatility-seen-2015-07-31), Chinese stocks fell, putting a cap on their .

The reaction to the wage data added to the rally that began on Thursday on so-called end-of-month index extension buying--a form of technical buying that occurs because bond portfolios that track indexes need to be rebalanced at the end of the month.

The rebalancing is done to reflect changes in the index due to the issuance of new bonds on one hand and coupon payments and redemptions on the other.

In Europe, government bond yields were slightly lower on Friday after a big drop in German retail sales added to Thursday's mixed economic data that pointed to subdued annual inflation and slow growth in the labor market. The yield on the benchmark German 10-year bund inched 0.1 basis point lower to 0.612%.

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