US equity indexes declined in midday trading Friday following a drop in government bond yields after a consumer sentiment gauge was revised lower and private sector output growth unexpectedly slowed.

The Nasdaq Composite slumped 1.4% to 19,689.7, with the S&P 500 down 1.1% to 6,051.2 and the Dow Jones Industrial Average 1.3% lower at 43,603.9. All peer groups were in the red intraday, with consumer discretionary and industrials leading the decliners. The consumer staples sector was the sole gainer.

In economic news, the University of Michigan consumer sentiment index was revised downward on Friday to 64.7 for February from 67.8 in the preliminary estimate, compared with expectations for no revision in a survey compiled by Bloomberg. That latest print was below the upwardly revised final reading of 71.7 in January.

Respondents in the Michigan survey expected a 4.3% inflation rate over the next year and 3.5% annual inflation over the next five years, up from 3.3% and 3.2%, respectively, in January.

Output growth in the US private sector unexpectedly slowed in February as the services sector contracted, while optimism waned amid worries over the impact of tariffs and domestic spending cuts, S&P Global's (SPGI) flash purchasing managers' index showed. The composite output gauge fell to a 17-month low of 50.4 from 52.7 in January, compared with the 53.2 consensus in a survey compiled by Bloomberg.

The pace of annual rates for seasonally adjusted US existing home sales fell to 4.08 million in January from 4.29 million in December, compared with the 4.13 million expected in a survey compiled by Bloomberg, data from the National Association of Realtors showed. Sales were up 2% from a year earlier.

US Treasury yields fell, with the 10-year down 6.8 basis points to 4.43% and the two-year was 3.8 basis points lower at 4.23%.

Further, in economic news, the February flash reading of manufacturing conditions from S&P Global Friday rose to an eight-month high of 51.6 from 51.2 in January, above an expected 51.4 in a survey compiled by Bloomberg. The index indicates expansion, in line with the Empire State and the Philadelphia Fed manufacturing readings released earlier in the week.

In company news, UnitedHealth Group (UNH) is under scrutiny by the US Department of Justice for allegedly encouraging doctors to record diagnoses that result in extra payments to the insurer's "Medicare Advantage" plans, the Wall Street Journal reported Friday, citing people familiar with the matter. Shares of the company slumped 8.8%, among the worst performers on the S&P 500.

Akamai Technologies (AKAM) has "limited" short-term growth opportunities, BofA Securities said in a note Friday, following the company's Q4 results overnight. BofA downgraded Akamai to neutral from buy and cut its price target to $100 from $125. Akamai shares sank 19.6% intraday, the steepest decliner on the S&P 500.

MercadoLibre's (MELI) Q4 diluted earnings and sales late Thursday beat the average analyst estimate compiled by FactSet. Shares jumped 8.3% intraday, the top performer on the Nasdaq.

West Texas Intermediate crude oil futures slumped 2.1% to $70.97 a barrel.

Gold futures were fractionally lower at $2,955.4, and their silver counterparts dropped 1.2% to $33.4.