(The Center Square) — The "whipsaw effect" of President Donald Trump's tariffs is increasing or having no impact on imports at California ports despite widespread speculation.

One theory among economists has been that Trump’s tariffs could lead to a decrease in imports to the U.S. But the flow of goods into the ports of San Diego, Los Angeles and San Francisco have yet to be hindered by the tariffs, according to officials. The latest round is scheduled to take effect Thursday.

Gene Seroka, the executive director of the Port of Los Angeles, said the uncertainty of Trump’s tariffs is the cause for the increase of imports in June and possibly in July as well.

Nations around the world are working hard to push as many imports into the U.S. before more tariffs are placed, he said.

Seroka said during the port’s July cargo news briefing that the port had 892,340 container units in June, making it the port’s busiest June on record.

Of the total units, 470,450 units were imports, 126,144 units were exports and 295,746 were empty units.

Compared to June of last year, the Port of Los Angeles had an 8% increase in container units. The port had 827,757 total units, and of those units, 428,753 were imports, 122,515 were exports and 276,489 were empty containers.

The Port of Los Angeles has moved 4,995,811 units since the beginning of this year. This time last year, the port had moved 4,731,491 units.

Seroka attributed the increase in the number of containers to the “whipsaw effect” of Trump’s tariffs.

Seroka said that when tariffs on imports went into effect in May, imports at the Port of Los Angeles slowed down significantly through the first half of June. Seroka added that when some tariffs stopped in the middle of June, then cargo started moving again.

Seroka said he was expecting the port to have around 950,000 units in July, which would be one of the port’s top months.

The Port of Los Angeles told The Center Square the cargo units were still being counted and that the latest number won't be released until the cargo news briefing on Aug. 13. But the port said Seroka’s July projections are looking to be in line with the data seen so far.

Trump’s executive order on July 31 sets new tariffs that will start on Thursday. Seroka said he expects imports at the port to decrease after that.

"Looking into August, if everything holds the way we see it right now, I expect volume to ease because of those new tariffs being placed, making it more costly for American importers," he said.

Port of San Francisco spokesman Eric Young told The Center Square, “Recent tariffs have not affected the number of exports or imports of vehicles.”

Young, the port's director of communications, added that the port exported 9,686 vehicles and imported 18,835 vehicles last year. From the vehicles imported, 1,252 were Kia vehicles from South Korea and 17,583 were General Motor vehicles that were manufactured in Mexico.

The U.S tariff rate for Mexico is at 25% and the U.S. tariff rate for South Korea will be at 15%, starting Thursday.

The Port of San Diego operates four terminals, two of which are marine cargo terminals.

The National City Marine Terminal is San Diego' main marine cargo terminal. The terminal is the most advanced vehicle import and export facility on the West Coast, according to the Port of San Diego's official website. The terminal serves as the "primary port of entry for one out of every 10 new foreign cars" imported to the U.S.

Brianne Page, the port's public information officer, told The Center Square that the Port of San Diego and Pasha Automotive Services, which operates from the National City Marine Terminal, report they haven't seen any increase or decrease in vehicle imports cause by tariffs. The port and Pasha said they have, however, seen some slow recovery since the COVID-19 pandemic.

Cary Davis, president and CEO of the American Association of Port Authorities, spoke on NPR Monday about the impact of Trump's trade and tariff policies on U.S. ports. Davis said the U.S. is seeing a lot more products coming into its ports.

"We have a lot more volumes of cargo, freight, cars, materials, coming through our seaports and even our land borders," Davis said.

Davis also said the tariffs' "whipsaw effect" has made it hard for ports to know how much goods will be coming through.

"The whipsaw effect that's happening of the unpredictability of tariffs makes it really hard to plan for exactly how much free volume will be coming through the ports," Davis said.

When Trump's new set of tariffs start later in the week, U.S. ports and many Americans will be paying close attention whether imports actually decrease.