What happened

Rivian Automotive (RIVN -5.12%) stock is plummeting today, but it's not about anything the company told investors -- yet. Rivian shares were down 9.1% as of 11:48 a.m. ET Tuesday.

So what

The drop came after fellow EV start-up Lucid Group provided its quarterly update, and investors seem to fear that some of what it said will apply to Rivian as well. Rivian will provide investors with its fourth-quarter and full-year 2021 update next Thursday, March 10. 

Rivian R1S SUV in production at the company's Illinois manufacturing plant.

Rivian R1S SUV on the production line at the company's Illinois manufacturing plant. Image source: Rivian Automotive.

Now what

Lucid drastically dropped its projected 2022 production volume by up to 40% due to supply chain and logistics constraints. Lucid and Rivian are different companies with different products, but Rivian already had missed its own projections for its electric vehicle production in 2021. After telling investors it had planned to produce 1,200 vehicles, it was only able to finish the year with 1,105 produced and 920 delivered. 

Rivian is slightly further along in its development than Lucid. Rivian had more than 70,000 preorders for its pickup truck and SUV models as of the middle of December. Lucid said yesterday it currently has about 25,000 reservations for its luxury electric sedans. 

But Rivian has been looking ahead, and has already announced plans for a new, $5 billion manufacturing plant in Georgia that will have the annual capacity to produce 400,000 vehicles. At the same time, it is working on increasing the annual capacity at its existing Illinois plant from 150,000 to 200,000 vehicles. 

With those expansions already in the works, investors will likely be unhappy if Rivian mirrors Lucid with comments about supply chain problems and subsequent plans for lower production volumes this year. Some investors aren't waiting for that possible announcement to come before selling the stock.