I think two weeks is pretty much the low end of transit time for a container from China to US, so I wouldn't expect needing much modeling within that window.

Ships can be rerouted while in transit. I bet it is extremely unusual for a container ship, but we do live in interesting times.

There was an interview with a shipping manager somewhere (probably the 3-hour documentary by Gamers Nexus?). They said absolutely have been rerouting container ships in transit.

But these ships are carrying containers for many different companies, right?

If some companies want the goods now and other companies need to hold off, how does that work?

Just whoever's shipping the most goods wins?

Most container ships aren’t enormous behemoths

The more reasonable sized ones and the specialized ones (especially the car ones) often service a single buyer at a time

Container ships did get rerouted when that ship got stuck in the Suez Canal.

But that’s “same port, different route” rerouting right? Here you would have to have “different port” rerouting (or some really weird weather making the Pacific intransitable”

Cruising speed can also be modulated, easily within some ranges. You might speed up a little if you think you can land cargo before new tariffs, and you may slow if you think tariffs may be reduced if you land later. Staff costs for the vessel are relatively small, so as long as you don't go outside the range of speeds that are fuel efficient, there's flexibility.

Some of the tariff increases are so high that they effectively spoil the cargo; there's no point in bringing it through customs at those prices, and it typically won't make sense to ship it back, and it may not be possible to ship it elsewhere from the port either, so it is most likely to be destroyed at the port. Delaying to see if tariffs go down may be worthwhile for enough of the cargo that it makes sense to slow the whole boat.

Additionally, if demand for shipping is up, going faster allows for more supply, and if demand has slowed, going slower reduces supply.

The tariffs are based on departure not arrival date.

That's easy enough to fake. How is US customs going to know when a German company's ship registered in the Philippines left a Chinese port?

Presumably by asking the Chinese authorities directly? We have near instantaneous global communication these days - that's how I'm conversing with you right now.

There's also AIS

https://www.marinetraffic.com/en/ais/home/

Of course enabled by the very tech you mention.

There is a pretty huge amount of ship and satellite tracking these days

You’d just lie about which ship it was on.

While it's still in the shipping container with a GPS tracker on it?

I've very briefly worked with a team that was responsible for satellites that track ships and their AIS data, including trying to identify ships spoofing AIS though various means. (It was civilian, a university group, but I'm sure states have similar and more)

Do you have a source for this? Because from my own experience, and from everything I can find online, this is not true.

Tariffs are based on date of entry: https://www.vedderprice.com/remember-basic-import-rules-when... (see 'Rule 2')

It happens all the time but it’s more useful to think in terms of container flows getting rerouted. Container ships sail in fixed loops so have containers on board for multiple ports. It often happens that the order in which the ports are called (the rotation) is changed, or a particular port gets skipped all together. Reasons can be congestion, delays in previous ports, etc. etc. The line can choose to transship the cargo, so pick it up with a second ship to carry it to destination, have the customer pick it up in the new location (possibly with a rebate) or truck/rail it to the final destination themselves.

Yeah I was wondering if those models try to smooth those bumps.