Oil posted losses for two weeks in a row 

The Commerce Department reported Friday that the U.S. economy grew at a 0.7 percent annual rate in the first quarter, below Wall Street’s expectations for 1.2 percent growth.

Weaker-than-anticipated economic growth typically raises concern about energy and fuel consumption, weighing on crude prices. Oil “is the ultimate macroeconomic commodity,” in the words of Tom Kloza, global head of energy analysis at Oil Price Information Service.

And a study of oil’s moves around economic data shows there’s a lot of truth to that.

Since 2001, Commerce’s first of three readings on first-quarter gross domestic product undershot forecasts by up to 50 basis points on seven occasions. U.S. benchmark West Texas Intermediate crude traded lower five trading days after these releases 100 percent of the time, according to data crunched with trading analysis technology Kensho.

The median return for WTI over those seven instances was a negative 6.14 percent.

To be sure, historical studies don’t always guarantee future results, even ones with a perfect track record. And many economists have dismissed this first reading of economic growth as distorted by seasonal factors and believe it will be revised higher.

But this poor reading comes at a crucial time for crude. A meeting of the Organization of the Petroleum Exporting Countries on May 25, where the exporter group will decide whether to extend a six-month coordinated production cut aimed at balancing a global oil oversupply.

De facto OPEC boss Saudi Arabia and other Gulf producers have signaled support for an extension through the second half of 2017. But crude prices have nevertheless slipped from mid-April highs on concerns about weakness in the gasoline market, resurgent U.S. shale oil production and stubbornly high global crude stockpiles.

Signs this week that an OPEC extension is imminent could boost the market. But tepid gasoline demand and the return of sidelined Libyan oil production last week will make it difficult for OPEC to talk up the market in the coming days, according to Kloza.

“It’s going to be tough for that PR machine to really get something going before the actual meeting takes place,” he told CNBC.